Fix collapse setting for Django 5.1+

[IgorCode]

Django template reference: https://github.com/django/django/blob/stable/5.2.x/django/contrib/admin/templates/admin/includes/fieldset.html#L3

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.10%. Comparing base (777bdb8) to head (1614466).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #648   +/-   ##
=======================================
  Coverage   85.10%   85.10%           
=======================================
  Files          21       21           
  Lines         752      752           
  Branches      123      123           
=======================================
  Hits          640      640           
  Misses         81       81           
  Partials       31       31           

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