Update github workflow

Author: gonuit

.github/workflows/test.yml

@@ -7,7 +7,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
-      - uses: subosito/flutter-action@v1.4.0
+      - uses: subosito/flutter-action@v2.3.0
+        with:
+          channel: 'stable'
       - name: Getting packages
         run: flutter pub get
       - name: analyzis