docs: retention settings in garbage collector

[fykaa]

closes #5214

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 55.35%. Comparing base (d377139) to head (803ec20).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5489      +/-   ##
==========================================
+ Coverage   55.11%   55.35%   +0.24%     
==========================================
  Files         426      430       +4     
  Lines       31564    31851     +287     
==========================================
+ Hits        17396    17631     +235     
- Misses      13163    13214      +51     
- Partials     1005     1006       +1     

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