(re)moved MixedModelsExt traces

[behinger]

Related issues

Closes #

Checklist

• I am following the contributing guidelines
• Tests are passing
• Lint workflow is passing
• Docs were updated and workflow is passing

[codecov]

Codecov Report

Attention: Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.

Project coverage is 63.33%. Comparing base (015b6fa) to head (d9084d6).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/fit.jl	33.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #243      +/-   ##
==========================================
- Coverage   70.49%   63.33%   -7.16%     
==========================================
  Files          30       23       -7     
  Lines        1742     1361     -381     
==========================================
- Hits         1228      862     -366     
+ Misses        514      499      -15     

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