fix: negbinom consistency plots now have the correct boundaries

[pabloitu]

Fixes #236 typo/error in poisson_consistency_test that made negativebinomial critical intervals being reversely assigned, thus creating error with matplotlib.

pyCSEP Pull Request Checklist

Type of change:

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• I have performed a self-review of my own code
• New and existing unit tests pass locally with my changes

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (1e2badb) 54.95% compared to head (d887da2) 54.95%.

❗ Current head d887da2 differs from pull request most recent head 3101a2f. Consider uploading reports for the commit 3101a2f to get more accurate results

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Additional details and impacted files

@@           Coverage Diff           @@
##             main     #245   +/-   ##
=======================================
  Coverage   54.95%   54.95%           
=======================================
  Files          23       23           
  Lines        3963     3963           
  Branches      578      578           
=======================================
  Hits         2178     2178           
  Misses       1648     1648           
  Partials      137      137           

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[fabiolsilva]

Fixed reversed plow and phigh values to correct plot boundaries.

[fabiolsilva]

Fixed reversed plow and phigh values to correct plot boundaries.