Test update following WFSS FITS unit change

[tapastro]

Related to JP-3931

This PR follows from spacetelescope/stdatamodels#529 , which modified the unit string for WFSS tables. This updates the truth to get passing tests.

Tasks

• If you have a specific reviewer in mind, tag them.
• add a build milestone, i.e. Build 12.0 (use the latest build if not sure)
• Does this PR change user-facing code / API? (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)
  • update or add relevant tests
  • update relevant docstrings and / or docs/ page
  • start a regression test and include a link to the running job (click here for instructions)
    • Do truth files need to be updated ("okified")?
      • after the reviewer has approved these changes, run okify_regtests to update the truth files
• if a JIRA ticket exists, make sure it is resolved properly

[tapastro]

RTs: https://github.com/spacetelescope/RegressionTests/actions/runs/16372012604

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.37%. Comparing base (deeed5e) to head (b4b5e93).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #9667   +/-   ##
=======================================
  Coverage   80.37%   80.37%           
=======================================
  Files         367      367           
  Lines       37265    37265           
=======================================
  Hits        29951    29951           
  Misses       7314     7314           

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[emolter]

I think there are actually two instances of expected_units and you've only changed one of them. that's why the unit tests are still failing even when pointing to your stdatamodels branch

[tapastro]

Updated RT after getting the second degrees check fixed: https://github.com/spacetelescope/RegressionTests/actions/runs/16379943864

[emolter]

LGTM pending approval of the stdatamodels PR

don't forget to point stdatamodels back to main

all the regtest failures make sense, they're just pointing out the unit changes

[melanieclarke]

LGTM, pending merge of the stdatamodels PR and pyproject.toml update.

[zacharyburnett]

@meeseeksdev backport to release/1.19.x