fix: flutter analyze problems

frontend/app_flowy/packages/appflowy_editor/lib/src/render/selection_menu/selection_menu_widget.dart

@@ -2,7 +2,6 @@ import 'dart:math';
 
 import 'package:appflowy_editor/appflowy_editor.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:flutter/material.dart';
 import 'package:flutter/services.dart';
 

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

@@ -1,6 +1,5 @@
 import 'package:appflowy_editor/appflowy_editor.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:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 import '../../infra/test_editor.dart';

frontend/app_flowy/packages/appflowy_editor/test/service/internal_key_event_handlers/slash_handler_test.dart

@@ -1,6 +1,5 @@
 import 'package:appflowy_editor/appflowy_editor.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:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 import '../../infra/test_editor.dart';