Fix dimension ordering for traceplot with divergences

[sethaxen]

Description

Fixes #2150 by internally reordering dimensions of diverging as expected in plot_trace.

Checklist

• Does the PR follow official
  PR format?
• Does the PR include new or updated tests to prevent issue recurrence (using pytest fixture pattern)?
• Is the code style correct (follows pylint and black guidelines)?
• Is the fix listed in the Maintenance and fixes
  section of the changelog?

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📚 Documentation preview 📚: https://arviz--2151.org.readthedocs.build/en/2151/

[codecov]

Codecov Report

Merging #2151 (8e7c4b5) into main (d030d44) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #2151   +/-   ##
=======================================
  Coverage   90.73%   90.73%           
=======================================
  Files         118      118           
  Lines       12579    12579           
=======================================
  Hits        11413    11413           
  Misses       1166     1166           

Impacted Files	Coverage Δ
arviz/plots/traceplot.py	95.34% <100.00%> (ø)

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