Update isku.extract_regions docs

[brews]

User mentioned they wanted to extract regions without transformations. Based on their feedback, this PR is a quick update to docstrs so it's a bit easier for users to discover.

Basically, users can directly use isku.GridWeightingRegions.extract_regions() if they don't need pre and post processing transformations of isku.extract_regions().

Also updates zensical config so that function parameters don't appear in the API Reference docs table of contents.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.11%. Comparing base (e5cc904) to head (c11d60c).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #73   +/-   ##
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  Coverage   98.11%   98.11%           
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  Files           3        3           
  Lines          53       53           
=======================================
  Hits           52       52           
  Misses          1        1           

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[kemccusker]

Thanks, @brews, this is a helpful update

[brews]

Thank you very much for taking a look, @kemccusker .