Bump dart-lang/setup-dart from 1.3 to 1.4 (#208)

Bumps [dart-lang/setup-dart](https://github.com/dart-lang/setup-dart) from 1.3 to 1.4.
- [Release notes](https://github.com/dart-lang/setup-dart/releases)
- [Changelog](https://github.com/dart-lang/setup-dart/blob/main/CHANGELOG.md)
- [Commits](https://github.com/dart-lang/setup-dart/compare/6a218f2413a3e78e9087f638a238f6b40893203d...a57a6c04cf7d4840e88432aad6281d1e125f0d46)

---
updated-dependencies:
- dependency-name: dart-lang/setup-dart
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>