Update active tests

[OriolAbril]

Dropping beanmachine we also are able to use latest black, instead
of the over a year old version beanmachine pulls as runtime
dependency.

I also want to fix the readthedocs build in this PR.

Checklist

• Follows official PR format
• Includes a sample plot to visually illustrate the changes (only for plot-related functions)
• New features are properly documented (with an example if appropriate)?
• Includes new or updated tests to cover the new feature
• Code style correct (follows pylint and black guidelines)
• Changes are listed in changelog

---

📚 Documentation preview 📚: https://arviz--2290.org.readthedocs.build/en/2290/

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (eb88f3a) 86.89% compared to head (cb21419) 86.70%.
Report is 2 commits behind head on main.

Files	Patch %	Lines
arviz/data/io_pyjags.py	0.00%	2 Missing ⚠️
arviz/data/io_beanmachine.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2290      +/-   ##
==========================================
- Coverage   86.89%   86.70%   -0.20%     
==========================================
  Files         122      122              
  Lines       12628    12640      +12     
==========================================
- Hits        10973    10959      -14     
- Misses       1655     1681      +26     

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[ahartikainen]

LGTM

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