Fix branch coverage

[marcpaterno]

Description

This PR provides commits to improve the branch coverage of the test suite.
It also activates the pytest measurement of branch coverage.

Type of change

Please delete the bullet items below that do not apply to this pull request.

• Refactoring

Checklist:

The following checklist will make sure that you are following the code style and
guidelines of the project as described in the
contributing page.

• I have run bash pre-commit-check and fixed any issues
• I have added tests that prove my fix is effective or that my feature works
• I have made corresponding changes to the documentation
• I have 100% test coverage for my changes (please check this after the CI system has verified the coverage)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.0%. Comparing base (8d443c2) to head (d720675).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #482   +/-   ##
=======================================
  Coverage   100.0%   100.0%           
=======================================
  Files          54       55    +1     
  Lines        4167     4203   +36     
=======================================
+ Hits         4167     4203   +36     

Files with missing lines	Coverage Δ
firecrown/ccl_factory.py	100.0% <100.0%> (ø)
firecrown/connector/cobaya/likelihood.py	100.0% <ø> (ø)
firecrown/connector/cosmosis/likelihood.py	100.0% <100.0%> (ø)
firecrown/connector/mapping.py	100.0% <100.0%> (ø)
firecrown/connector/numcosmo/helpers.py	100.0% <100.0%> (ø)
firecrown/connector/numcosmo/numcosmo.py	100.0% <100.0%> (ø)
firecrown/data_functions.py	100.0% <100.0%> (ø)
firecrown/likelihood/factories.py	100.0% <100.0%> (ø)
firecrown/likelihood/two_point.py	100.0% <100.0%> (ø)
firecrown/updatable.py	100.0% <100.0%> (ø)
... and 1 more

[marcpaterno]

See individual requests in the comments.