expose pygam model penalties via spline_kwargs fixes #1126

[bfurtwa]

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Description

Expose pygam model penalties via spline_kwargs. Before it was set to penalties=["derivative", "l2"] in the code. Now, the user can change the default by using: spline_kwargs={'penalties':['derivative']}

How has this been tested?

Tested with my own data pipeline. Does not change default parameter.

Closes

closes #1126

[codecov]

Codecov Report

Merging #1132 (b8038a7) into main (c3ced63) will decrease coverage by 1.24%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1132      +/-   ##
==========================================
- Coverage   80.63%   79.39%   -1.24%     
==========================================
  Files          51       51              
  Lines        8483     8483              
  Branches     2218     1645     -573     
==========================================
- Hits         6840     6735     -105     
- Misses       1101     1205     +104     
- Partials      542      543       +1     

Files	Coverage Δ
src/cellrank/models/_pygam_model.py	91.83% <ø> (ø)

... and 6 files with indirect coverage changes

[michalk8]

Thanks a lot @bfurtwa ! Failing tests are related to #1128 , will be dealt with later.