Updated miniconda version in GH Actions

[rickecon]

This PR updates the miniconda installer version to miniconda instead of mambaforge in our GitHub Actions. See Issue #124. Mambaforge is being deprecated and will begin to cause more and more onerous problems and delays in our GH Actions until January 2025 when it will completely stop working (see this blog post "Sunsetting Mambaforge").

The change is one line in three GH Actions, as recommended in the setup-miniconda README.md.

cc: @jdebacker

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 45.22%. Comparing base (a504ff6) to head (c8dd7f2).
Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #125   +/-   ##
=======================================
  Coverage   45.22%   45.22%           
=======================================
  Files          18       18           
  Lines        1404     1404           
=======================================
  Hits          635      635           
  Misses        769      769           

Flag	Coverage Δ
unittests	45.22% <ø> (ø)

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