Use new setup actions (dart-lang/web_socket_channel#153)

pkgs/web_socket_channel/.github/workflows/test-package.yml

diff --git a/pkgs/web_socket_channel/.github/workflows/test-package.yml b/pkgs/web_socket_channel/.github/workflows/test-package.yml
index e958231..6d84019 100644
--- a/pkgs/web_socket_channel/.github/workflows/test-package.yml
+++ b/pkgs/web_socket_channel/.github/workflows/test-package.yml
@@ -1,4 +1,4 @@
-name: Dart CI
+name: CI
 
 on:
   # Run on PRs and pushes to the default branch.
@@ -14,23 +14,17 @@
 
 jobs:
   # Check code formatting and static analysis on a single OS (linux)
-  # against Dart dev and 2.10.0.
+  # against Dart dev and stable.
   analyze:
     runs-on: ubuntu-latest
     strategy:
-      fail-fast: false
       matrix:
         sdk: [dev]
-        version: [latest]
-        include:
-          - sdk: stable
-            version: 2.10.0
     steps:
       - uses: actions/checkout@v2
-      - uses: cedx/setup-dart@v2 # TODO(dart-lang/setup-dart#3): use the official setup-dart action
+      - uses: dart-lang/setup-dart@v0.5
         with:
-          release-channel: ${{ matrix.sdk }}
-          version: ${{ matrix.version }}
+          sdk: ${{ matrix.sdk }}
       - id: install
         name: Install dependencies
         run: dart pub get
@@ -38,32 +32,22 @@
         run: dart format --output=none --set-exit-if-changed .
         if: always() && steps.install.outcome == 'success'
       - name: Analyze code
-        run: dart analyze --fatal-infos
+        run: dart analyze
         if: always() && steps.install.outcome == 'success'
 
-  # Run tests on a matrix consisting of two dimensions:
-  # 1. OS: ubuntu-latest, (macos-latest, windows-latest)
-  # 2. release channel: dev, stable
   test:
     needs: analyze
     runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: false
       matrix:
-        # Add macos-latest and/or windows-latest if relevant for this package.
         os: [ubuntu-latest]
-        sdk: [dev]
-        version: [latest]
-        include:
-          - os: ubuntu-latest
-            sdk: stable
-            version: 2.10.0
+        sdk: [stable, dev]
     steps:
       - uses: actions/checkout@v2
-      - uses: cedx/setup-dart@v2 # TODO(dart-lang/setup-dart#3): use the official setup-dart action
+      - uses: dart-lang/setup-dart@v0.5
         with:
-          release-channel: ${{ matrix.sdk }}
-          version: ${{ matrix.version }}
+          sdk: ${{ matrix.sdk }}
       - id: install
         name: Install dependencies
         run: dart pub get
@@ -71,5 +55,5 @@
         run: dart test --platform vm
         if: always() && steps.install.outcome == 'success'
       - name: Run Chrome tests
-        run: dart test --platform chrome -j1
+        run: dart test --platform chrome
         if: always() && steps.install.outcome == 'success'