backup always print the warning log

[Leavrth]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. backup

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

3. What did you see instead (Required)

the warning log is print after backup done.

[WARN] [safe_point.go:88] ["service GC safe point lost, we may fail to back up if GC lifetime isn't long enough"] [lastSafePoint=452290088544763904] [safePoint="{ID=br-3cdd196c-e822-4076-bfd1-80f932dbc433,TTL=0s,BackupTime=\"2024-09-03 14:00:48.441 +0800 CST\",BackupTS=452288380519317508}"]

4. What is your TiDB version? (Required)