Downgrade to Flutter v3.19.3 (#1495)

.github/workflows/mobile-internal-release.yml

@@ -4,7 +4,7 @@ on:
     workflow_dispatch: # Allow manually running the action
 
 env:
-    FLUTTER_VERSION: "3.19.5"
+    FLUTTER_VERSION: "3.19.3"
 
 jobs:
     build: