Fix wcs api call in tests

[WilliamJamieson]

There are failures detected by the CI when using the dev version of GWCS. These are due to an incorrect call to the GWCS API that happened to work before when constructing test data. This PR fixes that for the tests.

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 below for change types)
  • run regression tests with this branch installed ("git+https://github.com/<fork>/stcal@<branch>")
    • jwst regression test
    • romancal regression test

news fragment change types...

• changes/<PR#>.apichange.rst: change to public API
• changes/<PR#>.bugfix.rst: fixes an issue
• changes/<PR#>.general.rst: infrastructure or miscellaneous change

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 29.57%. Comparing base (35726e9) to head (875357a).
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #332   +/-   ##
=======================================
  Coverage   29.57%   29.57%           
=======================================
  Files          36       36           
  Lines        7949     7949           
=======================================
  Hits         2351     2351           
  Misses       5598     5598           

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