TST: Turn unhandled warnings into exceptions

[pllim]

Closes #150

This PR addresses warnings.

Tasks

• update or add relevant tests
• update relevant docstrings and / or docs/ page
• Does this PR change any API used downstream? (if not, label with no-changelog-entry-needed)
  • write news fragment(s) in changes/: echo "changed something" > changes/<PR#>.<changetype>.rst (see changelog readme for instructions)
  • run regression tests with this branch installed ("git+https://github.com/<fork>/stcal@<branch>")
    • jwst regression test
    • romancal regression test

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.46%. Comparing base (4056166) to head (bf832b8).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #439      +/-   ##
==========================================
- Coverage   89.67%   89.46%   -0.21%     
==========================================
  Files          67       67              
  Lines       10447    10453       +6     
==========================================
- Hits         9368     9352      -16     
- Misses       1079     1101      +22     

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[pllim]

Kinda amazing you can still boast 80% coverage when CI is so red lol