build: update dependency on flutterfire_gen_utils

Author: kosukesaigusa

packages/flutterfire_gen/pubspec.yaml

@@ -13,7 +13,7 @@ dependencies:
   flutter:
     sdk: flutter
   flutterfire_gen_annotation: ^0.4.1
-  flutterfire_gen_utils: ^0.4.1
+  flutterfire_gen_utils: ^0.5.0
   json_annotation: ^4.8.1
   meta: ^1.9.1
   path: ^1.8.3