docs: hide deprecated options in README

[henryiii]

Just kept them around for a bit.

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 82.01%. Comparing base (2942230) to head (d7e0292).
Report is 78 commits behind head on main.

Files with missing lines	Patch %	Lines
src/scikit_build_core/settings/skbuild_docs.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #792   +/-   ##
=======================================
  Coverage   82.00%   82.01%           
=======================================
  Files          68       68           
  Lines        3935     3936    +1     
=======================================
+ Hits         3227     3228    +1     
  Misses        708      708           

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