Change cupertinoActivitYIndicator to cicularProgressIndicator

Signed-off-by: Sahil Kumar <[email protected]>

lib/src/message_list_view.dart

@@ -592,7 +592,7 @@ class _MessageListViewState extends State<MessageListView> {
           return Center(
             child: Padding(
               padding: const EdgeInsets.all(8.0),
-              child: const CupertinoActivityIndicator(),
+              child: const CircularProgressIndicator(),
             ),
           );
         });