Fixed language generation from build script

frontend/scripts/makefile/flutter.toml

@@ -181,7 +181,7 @@ script = [
   flutter clean
   flutter pub get
   flutter pub run easy_localization:generate -S assets/translations/
-  flutter pub run easy_localization:generate -f keys -o locale_keys.g.dart -S assets/translations  
+  flutter pub run easy_localization:generate -f keys -o locale_keys.g.dart -S assets/translations -s en.json
   """,
 ]
 script_runner = "@shell"