Fix python dependency issues with Python 3.12 and add to docs

[odunbar]

Purpose

Closes #317

Content

• update buildkite and testing to Python 3.12-compatible scipy (v1.14.1) and scikitlearn (v1.5.1)
• removed matplotlib (we do not need this?)
• add this update and other installation help in docs page

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• I have read and checked the items on the review checklist.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.57%. Comparing base (acf1051) to head (434413e).
Report is 22 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #319      +/-   ##
==========================================
+ Coverage   88.17%   88.57%   +0.40%     
==========================================
  Files           8        8              
  Lines        1184     1217      +33     
==========================================
+ Hits         1044     1078      +34     
+ Misses        140      139       -1     

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[odunbar]

tests and buildkite now all pass, docs look good.