fix ground test docs schema list

[braingram]

The schema list in the ground tests docs isn't rendering:
https://rad.readthedocs.io/en/latest/ground_tests.html

This PR fixes the formatting to allow them to render:
https://rad--447.org.readthedocs.build/en/447/ground_tests.html

Closes: #444

Tasks

• Update or add relevant rad tests.
• Update relevant docstrings and / or docs/ page.
• Does this PR change any schema files?
  • Schema changes were discussed at RAD Review Board meeting.
• 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).
  • Start a romancal regression test (https://github.com/spacetelescope/RegressionTests/actions/workflows/romancal.yml) with this branch installed ("git+https://github.com/<fork>/rad@<branch>").
  • Update relevant roman_datamodels utilities and tests.

News fragment change types:

• changes/<PR#>.feature.rst: new feature
• changes/<PR#>.bugfix.rst: fixes an issue
• changes/<PR#>.doc.rst: documentation change
• changes/<PR#>.removal.rst: deprecation or removal of public API
• changes/<PR#>.misc.rst: infrastructure or miscellaneous change

[braingram]

I'd say this doesn't need a changelog but can't add the label. If a changelog is preferred let me know.

Pinging @PaulHuwe for review.

[PaulHuwe]

Great!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.45%. Comparing base (c1811ab) to head (922862a).
Report is 187 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #447      +/-   ##
==========================================
+ Coverage   95.38%   95.45%   +0.06%     
==========================================
  Files           4        4              
  Lines         195      198       +3     
==========================================
+ Hits          186      189       +3     
  Misses          9        9              

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[PaulHuwe]

The second part of this PR is fixing #444