👌 Remove duplicate CSS hashing for sphinx >= 7.1

[chrisjsewell]

Since sphinx v7.1, a checksum is already added to the CSS file URL, so hashing the content is no longer necessary (see sphinx-doc/sphinx#11415)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.18%. Comparing base (be1b85d) to head (fbb402b).
Report is 10 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #193      +/-   ##
==========================================
+ Coverage   89.15%   89.18%   +0.03%     
==========================================
  Files          11       11              
  Lines         959      962       +3     
==========================================
+ Hits          855      858       +3     
  Misses        104      104              

Flag	Coverage Δ
pytests	89.18% <100.00%> (+0.03%)	⬆️

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