fix: align pitr backup retention with cluster retentionPeriod in back…

[fengluodb]

…up schedule

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 65.01%. Comparing base (2b456ec) to head (a465d3c).
Report is 4 commits behind head on release-0.9.

Files with missing lines	Patch %	Lines
...trollers/apps/transformer_cluster_backup_policy.go	0.00%	3 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##           release-0.9    #8410      +/-   ##
===============================================
+ Coverage        64.81%   65.01%   +0.20%     
===============================================
  Files              358      358              
  Lines            45428    45459      +31     
===============================================
+ Hits             29445    29557     +112     
+ Misses           13349    13283      -66     
+ Partials          2634     2619      -15     

Flag	Coverage Δ
unittests	65.01% <0.00%> (+0.20%)	⬆️

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