💚 Fix CI flutter version incorrect

.github/workflows/nightly.yml

@@ -13,7 +13,7 @@ jobs:
       - name: Set up Flutter
         uses: subosito/flutter-action@v2
         with:
-          channel: stable
+          channel: master
           cache: true
       - run: flutter pub get
       - run: flutter build web --release --base-href=/