dumping 失败提示:stop fetching the pending tso requests due to context canceled

备份完成后,通过 PD 来启动 GC safepoint (备份过程中 GC safepoint 是停掉的),备份完成 context cancel 引起的这个 ERROR,后续版本会优化相关日志和逻辑。

Bug 详情请见:https://github.com/pingcap/tidb/issues/31335