Fix deprecated codecov action parameter use and limit sphinx in documentation rendering

[djhoese]

Replacement for #3068. In that PR I started updating sphinx usage to 8.2.0 and then realized there is a memory leak in 8.2.0 that causes RTD builds to fail. In this PR I keep the CI warning fix, but limit sphinx so 8.2.0 isn't used.

• Closes #xxxx
• Tests added
• Fully documented
• Add your name to AUTHORS.md if not there already

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.11%. Comparing base (17cf0ce) to head (aecf736).
Report is 407 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3071      +/-   ##
==========================================
- Coverage   96.14%   96.11%   -0.04%     
==========================================
  Files         383      383              
  Lines       55785    55685     -100     
==========================================
- Hits        53636    53523     -113     
- Misses       2149     2162      +13     

Flag	Coverage Δ
behaviourtests	3.88% <ø> (+<0.01%)	⬆️
unittests	96.21% <ø> (-0.04%)	⬇️

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[djhoese]

I'm going to close this. It shouldn't be needed now that sphinx was patched. #3068 should be the PR to be merged.