use main branch for setup-dart

Author: isoos

.github/workflows/pub-publish.yml

@@ -22,7 +22,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
-      - uses: dart-lang/setup-dart
+      - uses: dart-lang/setup-dart@main
       - name: Install dependencies
         run: dart pub get
         working-directory: ${{ inputs.working-directory }}