Update docstrings again

[marcpaterno]

This updates more docstrings (and some type annotations).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.3%. Comparing base (71504b5) to head (90b83aa).
Report is 13 commits behind head on master.

Additional details and impacted files

@@          Coverage Diff           @@
##           master    #429   +/-   ##
======================================
  Coverage    98.3%   98.3%           
======================================
  Files          47      47           
  Lines        3352    3356    +4     
======================================
+ Hits         3296    3300    +4     
  Misses         56      56           

Files with missing lines	Coverage Δ
firecrown/connector/cobaya/ccl.py	100.0% <100.0%> (ø)
firecrown/connector/cobaya/likelihood.py	100.0% <100.0%> (ø)
firecrown/connector/cosmosis/likelihood.py	97.3% <100.0%> (+<0.1%)	⬆️
firecrown/connector/mapping.py	100.0% <100.0%> (ø)
firecrown/generators/inferred_galaxy_zdist.py	100.0% <ø> (ø)