build(deps): bump dart-lang/setup-dart in the github-actions group (#539)

Bumps the github-actions group with 1 update: [dart-lang/setup-dart](https://github.com/dart-lang/setup-dart).

Updates `dart-lang/setup-dart` from 1.7.2 to 1.8.1
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a href="https://github.com/dart-lang/setup-dart/releases">dart-lang/setup-dart's releases</a>.</em></p>
<blockquote>
<h2>v1.8.1</h2>
<ul>
<li>Update workflows to pin <code>actions/checkout</code> to a commit SHA.</li>
<li>Harden workflow permissions to <code>contents: read</code>.</li>
<li>Update <code>publish.yml</code> reusable workflow to reference <code>setup-dart@v1.8.0</code> and latest <code>setup-flutter</code>.</li>
<li>Bump <code>undici</code> to <code>6.28.0</code> and <code>@vercel/ncc</code> to <code>0.44.1</code>.</li>
</ul>
<h2>v1.8.0</h2>
<ul>
<li>Add a problem matcher for <code>dart analyze</code> to automatically create inline annotations on GitHub pull requests.</li>
<li>Update <code>publish.yml</code> reusable workflow to reference <code>setup-dart@v1.7.2</code> (running on Node 24) (<a href="https://redirect.github.com/dart-lang/setup-dart/issues/188">#188</a>[]).</li>
<li>Update GitHub Action dependencies (<code>actions/checkout</code> v7).</li>
<li>Bump <code>undici</code> to <code>6.27.0</code> and update npm dependencies.</li>
</ul>
<p><a href="https://redirect.github.com/dart-lang/setup-dart/issues/188">#188</a>: <a href="https://redirect.github.com/dart-lang/setup-dart/issues/188">dart-lang/setup-dart#188</a></p>
</blockquote>
</details>
<details>
<summary>Changelog</summary>
<p><em>Sourced from <a href="https://github.com/dart-lang/setup-dart/blob/main/CHANGELOG.md">dart-lang/setup-dart's changelog</a>.</em></p>
<blockquote>
<h2>v1.8.1</h2>
<ul>
<li>Update workflows to pin <code>actions/checkout</code> to a commit SHA.</li>
<li>Harden workflow permissions to <code>contents: read</code>.</li>
<li>Update <code>publish.yml</code> reusable workflow to reference <code>setup-dart@v1.8.0</code> and latest <code>setup-flutter</code>.</li>
<li>Bump <code>undici</code> to <code>6.28.0</code> and <code>@vercel/ncc</code> to <code>0.44.1</code>.</li>
</ul>
<h2>v1.8.0</h2>
<ul>
<li>Add a problem matcher for <code>dart analyze</code> to automatically create inline annotations on GitHub pull requests.</li>
<li>Update <code>publish.yml</code> reusable workflow to reference <code>setup-dart@v1.7.2</code> (running on Node 24) (<a href="https://redirect.github.com/dart-lang/setup-dart/issues/188">#188</a>[]).</li>
<li>Update GitHub Action dependencies (<code>actions/checkout</code> v7).</li>
<li>Bump <code>undici</code> to <code>6.27.0</code> and update npm dependencies.</li>
</ul>
<p><a href="https://redirect.github.com/dart-lang/setup-dart/issues/188">#188</a>: <a href="https://redirect.github.com/dart-lang/setup-dart/issues/188">dart-lang/setup-dart#188</a></p>
<h2>v1.7.2</h2>
<ul>
<li>Update Node.js requirement to Node 24.</li>
<li>Fix open Dependabot alerts by bumping <code>undici</code> to <code>&gt;=6.24.0</code>.</li>
<li>Update GitHub Action dependencies (<code>@actions/core</code>, <code>@actions/exec</code>, <code>@actions/tool-cache</code>, <code>@actions/http-client</code>).</li>
<li>Update workflow actions to their latest versions (<code>actions/checkout</code> v6, <code>setup-flutter</code>).</li>
</ul>
<h2>v1.7.1</h2>
<ul>
<li>Roll <code>undici</code> dependency to address <a href="https://github.com/nodejs/undici/security/advisories/GHSA-c76h-2ccp-4975">CVE-2025-22150</a>.</li>
<li>Update to the latest npm dependencies.</li>
<li>Recompile the action using the new Dart / JavaScript interop.</li>
</ul>
<h2>v1.7.0</h2>
<ul>
<li>
<p>Install flutter sdk in publishing step, allowing Flutter packages to be
published (<a href="https://redirect.github.com/dart-lang/setup-dart/issues/68">#68</a>[])</p>
<p><a href="https://redirect.github.com/dart-lang/setup-dart/issues/68">#68</a>: <a href="https://redirect.github.com/dart-lang/setup-dart/issues/68">dart-lang/setup-dart#68</a></p>
</li>
</ul>
<h2>v1.6.5</h2>
<ul>
<li>Fix zip path handling on Windows 11 (<a href="https://redirect.github.com/dart-lang/setup-dart/issues/118">#118</a>[])</li>
</ul>
<p><a href="https://redirect.github.com/dart-lang/setup-dart/issues/118">#118</a>: <a href="https://redirect.github.com/dart-lang/setup-dart/issues/118">dart-lang/setup-dart#118</a></p>
<h2>v1.6.4</h2>
<ul>
<li>Rebuild JS code.</li>
</ul>
<h2>v1.6.3</h2>
</blockquote>
<p>... (truncated)</p>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a href="https://github.com/dart-lang/setup-dart/commit/6afc89df92d6eb3834022f73cd65adc8cdfcb92d"><code>6afc89d</code></a> Pin actions/checkout to a commit SHA and harden workflow permissions (<a href="https://redirect.github.com/dart-lang/setup-dart/issues/196">#196</a>)</li>
<li><a href="https://github.com/dart-lang/setup-dart/commit/b653b3cfefb8a28264680eac1d50028789184290"><code>b653b3c</code></a> Prepare v1.8.1 release (<a href="https://redirect.github.com/dart-lang/setup-dart/issues/195">#195</a>)</li>
<li><a href="https://github.com/dart-lang/setup-dart/commit/45165d2ee1360cec3b96db808cfed1ac276dd71a"><code>45165d2</code></a> Bump the github-actions group across 1 directory with 2 updates (<a href="https://redirect.github.com/dart-lang/setup-dart/issues/194">#194</a>)</li>
<li><a href="https://github.com/dart-lang/setup-dart/commit/9af6bba6fc903c8d3427e54f6bef88b1cb519a77"><code>9af6bba</code></a> Pin actions/checkout to a commit SHA in publish.yml (<a href="https://redirect.github.com/dart-lang/setup-dart/issues/193">#193</a>)</li>
<li><a href="https://github.com/dart-lang/setup-dart/commit/ddca5d2081d05961010a263feb54fba5a01e4fb8"><code>ddca5d2</code></a> Bump <code>@​vercel/ncc</code> in the npm-dependencies group across 1 directory (<a href="https://redirect.github.com/dart-lang/setup-dart/issues/185">#185</a>)</li>
<li><a href="https://github.com/dart-lang/setup-dart/commit/5c116a34f6a4c3b222192b56c5440d03fc813d96"><code>5c116a3</code></a> Bump undici from 6.27.0 to 6.28.0 (<a href="https://redirect.github.com/dart-lang/setup-dart/issues/190">#190</a>)</li>
<li><a href="https://github.com/dart-lang/setup-dart/commit/7654d458321ee25acccccfdb86cd48bd95768ff1"><code>7654d45</code></a> chore: prepare v1.8.0 release (<a href="https://redirect.github.com/dart-lang/setup-dart/issues/188">#188</a>) (<a href="https://redirect.github.com/dart-lang/setup-dart/issues/189">#189</a>)</li>
<li><a href="https://github.com/dart-lang/setup-dart/commit/43c102f4dc9b9829c862401f0b64c7c9184eab4e"><code>43c102f</code></a> Bump actions/checkout from 6 to 7 in the github-actions group (<a href="https://redirect.github.com/dart-lang/setup-dart/issues/184">#184</a>)</li>
<li><a href="https://github.com/dart-lang/setup-dart/commit/10b57efefac07722403c8b9c95fa68bb09276def"><code>10b57ef</code></a> Bump the npm-dependencies group across 1 directory with 2 updates (<a href="https://redirect.github.com/dart-lang/setup-dart/issues/179">#179</a>)</li>
<li><a href="https://github.com/dart-lang/setup-dart/commit/a73965b3c99b30eb092908ce56c429eff91f9634"><code>a73965b</code></a> Bump undici from 6.24.1 to 6.27.0 (<a href="https://redirect.github.com/dart-lang/setup-dart/issues/182">#182</a>)</li>
<li>Additional commits viewable in <a href="https://github.com/dart-lang/setup-dart/compare/65eb853c7ba17dde3be364c3d2858773e7144260...6afc89df92d6eb3834022f73cd65adc8cdfcb92d">compare view</a></li>
</ul>
</details>
<br />

[![Dependabot compatibility score](https://dependabot-badges.githubapp.com/badges/compatibility_score?dependency-name=dart-lang/setup-dart&package-manager=github_actions&previous-version=1.7.2&new-version=1.8.1)](https://docs.github.com/en/github/managing-security-vulnerabilities/about-dependabot-security-updates#about-compatibility-scores)

Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting `@dependabot rebase`.

---

<details>
<summary>Dependabot commands and options</summary>
<br />

You can trigger Dependabot actions by commenting on this PR:
- `@dependabot rebase` will rebase this PR
- `@dependabot recreate` will recreate this PR, overwriting any edits that have been made to it
- `@dependabot show <dependency name> ignore conditions` will show all of the ignore conditions of the specified dependency
- `@dependabot ignore <dependency name> major version` will close this group update PR and stop Dependabot creating any more for the specific dependency's major version (unless you unignore this specific dependency's major version or upgrade to it yourself)
- `@dependabot ignore <dependency name> minor version` will close this group update PR and stop Dependabot creating any more for the specific dependency's minor version (unless you unignore this specific dependency's minor version or upgrade to it yourself)
- `@dependabot ignore <dependency name>` will close this group update PR and stop Dependabot creating any more for the specific dependency (unless you unignore this specific dependency or upgrade to it yourself)
- `@dependabot unignore <dependency name>` will remove all of the ignore conditions of the specified dependency
- `@dependabot unignore <dependency name> <ignore condition>` will remove the ignore condition of the specified dependency and ignore conditions

</details>