Remove soon to be deprecated jsonschema.RefResolver

[h-mayorquin]

Should close #1048.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.67%. Comparing base (64fb9e0) to head (eb8ff54).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1133      +/-   ##
==========================================
+ Coverage   90.58%   90.67%   +0.08%     
==========================================
  Files         128      129       +1     
  Lines        8011     8183     +172     
==========================================
+ Hits         7257     7420     +163     
- Misses        754      763       +9     

Flag	Coverage Δ
unittests	90.67% <100.00%> (+0.08%)	⬆️

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Files with missing lines	Coverage Δ
...on_specification/_yaml_conversion_specification.py	97.18% <100.00%> (+0.04%)	⬆️

... and 1 file with indirect coverage changes