remove manual setting of 2d kde lims

[OriolAbril]

Description

A few lines above we set x_x and y_y using the min and max along each dimension, so this has no visual effect on the plot, as long as you are plotting models independently. I think it is important to remove in order to allow using the kde mode of plot_pair to compare models. Otherwise only the last kde to be plotted is guaranteed to be seen complete, the rest are generally cut or lay completely outside the limits.

Checklist

• Does the PR follow official PR format?
• Does the PR include new or updated tests to prevent issue recurrence (using pytest fixture pattern)? No, could think of adding one, not sure if necessary
• Is the code style correct (follows pylint and black guidelines)?
• Is the fix listed in the Maintenance and fixes section of the changelog?

[codecov]

Codecov Report

Merging #1939 (3b126d4) into main (e4c9c8e) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1939      +/-   ##
==========================================
- Coverage   91.51%   91.49%   -0.02%     
==========================================
  Files         113      113              
  Lines       12231    12207      -24     
==========================================
- Hits        11193    11169      -24     
  Misses       1038     1038              

Impacted Files	Coverage Δ
arviz/plots/backends/bokeh/distplot.py	84.37% <100.00%> (-0.48%)	⬇️
arviz/plots/backends/bokeh/kdeplot.py	95.89% <100.00%> (-0.27%)	⬇️
arviz/plots/backends/bokeh/pairplot.py	86.95% <100.00%> (-0.55%)	⬇️
arviz/plots/backends/matplotlib/distplot.py	92.30% <100.00%> (-0.12%)	⬇️
arviz/plots/backends/matplotlib/kdeplot.py	98.85% <100.00%> (-0.04%)	⬇️
arviz/plots/backends/matplotlib/pairplot.py	91.93% <100.00%> (-0.17%)	⬇️
arviz/plots/plot_utils.py	89.03% <100.00%> (+0.19%)	⬆️

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[ahartikainen]

is there a possibility to check data limits?

Or does mpl this for us?

[OriolAbril]

both matplotlib and bokeh do that automatically, you can see in the example gallery preview for example how everything looks the same: https://arviz--1939.org.readthedocs.build/en/1939/examples/plot_pair_kde.html or https://arviz--1939.org.readthedocs.build/en/1939/examples/plot_pair_kde_hdi.html