chore: Remove DEFAULT_AUTO_FIELD from test settings

[fsbraun]

Removed the DEFAULT_AUTO_FIELD setting.

Description

Related resources

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Checklist

• I have opened this pull request against master
• I have added or modified the tests when changing logic
• I have followed the conventional commits guidelines to add meaningful information into the changelog
• I have read the contribution guidelines and I have joined #workgroup-pr-review on
  Slack to find a “pr review buddy” who is going to review my pull request.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (7a592fe) to head (0cdbec3).

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #113   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           11        11           
  Lines          147       147           
  Branches        19        19           
=========================================
  Hits           147       147           

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