Merge pull request #1157 from LucasXu0/remove_selection_menu_widget_test

chore: remove the selection_menu_widget_test.dart

Author: LucasXu0

frontend/app_flowy/packages/appflowy_editor/test/render/selection_menu/selection_menu_item_widget_test.dart

@@ -1,5 +1,4 @@
 import 'package:appflowy_editor/appflowy_editor.dart';
-import 'package:appflowy_editor/src/document/built_in_attribute_keys.dart';
 import 'package:appflowy_editor/src/render/selection_menu/selection_menu_item_widget.dart';
 import 'package:appflowy_editor/src/render/selection_menu/selection_menu_service.dart';
 import 'package:appflowy_editor/src/render/selection_menu/selection_menu_widget.dart';