fix: upgrade flutter action

Author: maxkrieger

.github/workflows/prerelease_ios.yml

@@ -31,7 +31,7 @@ jobs:
           java-version: "12.x"
 
       - name: Setup flutter
-        uses: subosito/flutter-action@v1
+        uses: subosito/flutter-action@v2
         with:
           channel: "stable"
           architecture: x64