Fix git submodule

.gitmodules

@@ -2,6 +2,10 @@
 	path = auth/thirdparty/sentry-dart
 	url = https://github.com/ente-io/sentry-dart.git
 	branch = sentry_flutter_ente
+[submodule "auth/flutter"]
+	path = auth/flutter
+	url = https://github.com/flutter/flutter.git
+	branch = stable
 [submodule "auth/assets/simple-icons"]
 	path = auth/assets/simple-icons
 	url = https://github.com/simple-icons/simple-icons.git