Goodness of fit fix

[plakrisenko]

What was displayed as Mean squared error, was't that.
Display Mean of squared normalized residuals instead

[plakrisenko]

Or better show MSE?

[codecov-commenter]

Codecov Report

❌ Patch coverage is 50.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.43%. Comparing base (7a60b2e) to head (c71f742).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
petab/v1/visualize/plot_residuals.py	50.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #473      +/-   ##
==========================================
- Coverage   75.46%   75.43%   -0.03%     
==========================================
  Files          62       62              
  Lines        6895     6899       +4     
  Branches     1227     1228       +1     
==========================================
+ Hits         5203     5204       +1     
- Misses       1221     1223       +2     
- Partials      471      472       +1     

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[dweindl]

Or better show MSE?

It might be nice to have different options, but I'm not sure what should be the default.