remove arviz dependency

[aloctavodia]

Description

Checklist

• Code style is correct (follows pylint and black guidelines)
• Includes new or updated tests to cover the new feature

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 90.55118% with 12 lines in your changes missing coverage. Please review.

Project coverage is 82.38%. Comparing base (f25da81) to head (d2b5140).

Files with missing lines	Patch %	Lines
preliz/internal/narviz.py	89.47%	8 Missing ⚠️
preliz/internal/plot_helper.py	69.23%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #536      +/-   ##
==========================================
+ Coverage   82.23%   82.38%   +0.15%     
==========================================
  Files         101      102       +1     
  Lines        8020     8136     +116     
==========================================
+ Hits         6595     6703     +108     
- Misses       1425     1433       +8     

Flag	Coverage Δ
	82.38% <90.55%> (?)

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