Add missing coverage configuration section to pyproject.toml

[djhoese]

CI was failing to upload coveralls for two reasons:

1. When we moved to pyproject.toml one of the config sections regarding coverage was forgotten.
2. A new security feature in git was causing the coveralls action to fail. I've fixed this upstream.

• Closes #xxxx
• Tests added
• Fully documented

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.95%. Comparing base (c9aabb7) to head (1742616).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2797   +/-   ##
=======================================
  Coverage   95.95%   95.95%           
=======================================
  Files         379      379           
  Lines       53861    53861           
=======================================
  Hits        51680    51680           
  Misses       2181     2181           

Flag	Coverage Δ
behaviourtests	4.09% <ø> (ø)
unittests	96.04% <ø> (ø)

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[mraspaud]

Thanks for fixing this!