chore: Use Cupertino Activity Indicator in ChatEventList

lib/pages/chat/chat_event_list.dart

@@ -1,3 +1,4 @@
+import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 
 import 'package:scroll_to_index/scroll_to_index.dart';
@@ -22,14 +23,10 @@ class ChatEventList extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final timeline = controller.timeline;
+
     if (timeline == null) {
-      return const Center(
-        child: CircularProgressIndicator.adaptive(
-          strokeWidth: 2,
-        ),
-      );
+      return const Center(child: CupertinoActivityIndicator());
     }
-
     final theme = Theme.of(context);
 
     final colors = [

lib/widgets/member_actions_popup_menu_button.dart

@@ -4,7 +4,6 @@ import 'package:flutter_gen/gen_l10n/l10n.dart';
 import 'package:matrix/matrix.dart';
 
 import 'package:fluffychat/widgets/permission_slider_dialog.dart';
-import 'adaptive_dialogs/show_modal_action_popup.dart';
 import 'adaptive_dialogs/show_ok_cancel_alert_dialog.dart';
 import 'adaptive_dialogs/show_text_input_dialog.dart';
 import 'adaptive_dialogs/user_dialog.dart';