GC safepoint not moving forward after log backup stopped

[3pointer]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. start log backup and pause it.
2. stop log backup.
3. check the service-gc-safepoint via pd-ctl.

2. What did you expect to see? (Required)

no br related service-gc-safepoint.

3. What did you see instead (Required)

4. What is your TiDB version? (Required)