[DOCS]: Update unclear clean docs

[rvandernoort]

Signed-by: Rover van der Noort s.r.vandernoort@student.tudelft.nl
Co-authored-by: Mark 16909269+Archmonger@users.noreply.github.com

Type of PR (feature, enhancement, bug fix, etc.)

Docs update

Description

Docs about clean were wrong and unclear, so I updated them with the docs from the code.

Fixes n.a.

Why should this be added

Explains the option better.

Checklist

• Documentation has been added or amended for this feature / update

[Archmonger]

Not a huge fan of the way the new description is written. Seems more confusing in a way.

[rvandernoort]

Updated the sentence wording which was hard to read, is it better like this? I think this wording actually reflects what the feature does.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (a8deb81) 91.22% compared to head (9b7cb15) 91.22%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #475   +/-   ##
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  Coverage   91.22%   91.22%           
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  Files          19       19           
  Lines         855      855           
  Branches      150      150           
=======================================
  Hits          780      780           
  Misses         40       40           
  Partials       35       35           

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[Archmonger]

Revisiting this PR now that our CI workflows are functional again.

I think your comment related to the "first day of the month" might not be valid anymore. I do see that the docstring within dbbackup.management.commands._base.BaseDbBackupCommand._cleanup_old_backups does say we do that. However, the source code for dbbackup.storage.Storage.clean_old_backups doesn't appear to differentiate between "first of the month" backups, and any other backup.

This PR can be merged after removing that comment in the docs, and fixing the incorrect docstring.