Bug in test_unused_thermal_cond due to pytest update

[KulaginVladimir]

Proposed changes

Due to new release of pytest (v8.0.0), test_unused_thermal_cond fails. The failure appears since pytest.warns(None) is depricated (since pytest v7.0.0rc1) and all PytestRemovedIn8Warning deprecation warnings are now errors by default (since pytest v8.0.0rc1). This PR modifies the test according to suggestions.

Types of changes

What types of changes does your code introduce to FESTIM?

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Code refactoring
• Documentation Update (if none of the other choices apply)
• New tests

Checklist

• Black formatted
• Unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (ada717a) 98.94% compared to head (41a24bb) 98.94%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #691   +/-   ##
=======================================
  Coverage   98.94%   98.94%           
=======================================
  Files          58       58           
  Lines        2181     2181           
=======================================
  Hits         2158     2158           
  Misses         23       23           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.