Minor fixes

[OriolAbril]

Description

This PR fixes bad numba usage we had been doing which recently started causing errors and warnings.
It also adds a numpy 2.0 cap to avoid issues once it is release (planned to happen around the
end of this year already).

I think this should be included in a patch release for 0.16. However, it would be nice if someone could test locally and confirm that indeed, the numba warnings are gone. cc @guin0x @ahartikainen might also be related to #2244

Checklist

• Follows official PR format
• Includes new or updated tests to cover the new feature
• Code style correct (follows pylint and black guidelines)
• Changes are listed in changelog

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📚 Documentation preview 📚: https://arviz--2268.org.readthedocs.build/en/2268/

[codecov]

Codecov Report

Merging #2268 (f6bd1b8) into main (a1cefcc) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #2268      +/-   ##
==========================================
+ Coverage   87.87%   87.90%   +0.03%     
==========================================
  Files         122      122              
  Lines       12458    12459       +1     
==========================================
+ Hits        10947    10952       +5     
+ Misses       1511     1507       -4     

Impacted Files	Coverage Δ
arviz/plots/backends/bokeh/forestplot.py	94.92% <100.00%> (ø)
arviz/plots/backends/bokeh/posteriorplot.py	98.36% <100.00%> (+0.01%)	⬆️
arviz/plots/backends/matplotlib/forestplot.py	97.86% <100.00%> (ø)
arviz/stats/density_utils.py	79.17% <100.00%> (ø)
arviz/stats/stats_utils.py	96.35% <100.00%> (ø)
arviz/utils.py	88.27% <100.00%> (ø)

... and 1 file with indirect coverage changes