Clarify the deletion frequency for gc controller

[allenxu404]

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Please add a summary of your change

Clarify there is the deletion frequency for gc controller so the effects of expiration are not applied immediately.

Does your change fix a particular issue?

Fixes #6245

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• Accepted the DCO. Commits without the DCO will delay acceptance.
• Created a changelog file or added /kind changelog-not-required as a comment on this pull request.
• Updated the corresponding documentation in site/content/docs/main.

[codecov-commenter]

Codecov Report

Merging #6414 (3bd423e) into main (ef443fe) will increase coverage by 0.03%.
The diff coverage is n/a.

❗ Current head 3bd423e differs from pull request most recent head c1ca9a0. Consider uploading reports for the commit c1ca9a0 to get more accurate results

@@            Coverage Diff             @@
##             main    #6414      +/-   ##
==========================================
+ Coverage   53.77%   53.81%   +0.03%     
==========================================
  Files         228      228              
  Lines       23777    23777              
==========================================
+ Hits        12787    12795       +8     
+ Misses      10043    10036       -7     
+ Partials      947      946       -1     

see 1 file with indirect coverage changes