[Mirror issue] 使用 Flutter 中国镜像的问题

### 问题镜像 URL

https://pub.flutter-io.cn/syncfusion_flutter_charts

### 错误内容截图或 log

502 Bad Gateway trying to find package syncfusion_flutter_charts at https://pub.flutter-io.cn.
Failed to update packages.


### pubspec.yaml

  syncfusion_flutter_charts: ^32.2.5


### 网络环境

公网，电信

### flutter doctor -v

_No response_