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 55.51%. Comparing base (ef1bd7e) to head (fb5da16).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5489   +/-   ##
=======================================
  Coverage   55.51%   55.51%           
=======================================
  Files         429      429           
  Lines       31954    31954           
=======================================
  Hits        17738    17738           
  Misses      13208    13208           
  Partials     1008     1008           

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