Update to next version of docs theme

[OriolAbril]

Still not ready to merge, it currently uses the theme from GitHub to test nothing breaks
with the change in minor version. After checking I will make a release of the theme and revert
pyproject.toml

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📚 Documentation preview 📚: https://causalpy--593.org.readthedocs.build/en/593/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.21%. Comparing base (dd7dfc4) to head (183b0fe).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #593   +/-   ##
=======================================
  Coverage   93.21%   93.21%           
=======================================
  Files          35       35           
  Lines        5511     5511           
  Branches      358      358           
=======================================
  Hits         5137     5137           
  Misses        246      246           
  Partials      128      128           

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