Update widget_test.yml

Author: boringdeveloper

.github/workflows/widget_test.yml

@@ -16,6 +16,6 @@ jobs:
         java-version: '12.x'
     - uses: subosito/flutter-action@v1
       with:
-        channel: 'latest'
+        channel: 'stable'
     - run: flutter pub get
     - run: flutter test