Hardcode Flutter version in GitHub action for now (until new Flutter works)

.github/workflows/release.yml

@@ -15,6 +15,9 @@ jobs:
       
       - uses: actions/checkout@v3
       - uses: subosito/flutter-action@v2
+        with:
+          channel: stable
+          flutter-version: 3.24.5
       - uses: actions/setup-java@v4
         with:
           distribution: 'temurin' # See 'Supported distributions' for available options