chore: rm unneeded dependencies

Author: russellwheatley

packages/firebase_ui_oauth_facebook/pubspec.yaml

@@ -20,8 +20,6 @@ dev_dependencies:
   flutter_test:
     sdk: flutter
   flutter_lints: ^3.0.1
-  mockito: ^5.4.4
-  build_runner: ^2.4.13
 
 # For information on the generic Dart part of this file, see the
 # following page: https://dart.dev/tools/pub/pubspec