JP-3899: Remove cube_skymatch

[emolter]

Resolves JP-3899

Closes #9231

This PR removes the unused cube skymatch step.

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

[emolter]

regression test started here https://github.com/spacetelescope/RegressionTests/actions/runs/14778281877

edit: all passing

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.57%. Comparing base (cabaee0) to head (e2c8621).
⚠️ Report is 690 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9426      +/-   ##
==========================================
+ Coverage   75.99%   76.57%   +0.58%     
==========================================
  Files         368      364       -4     
  Lines       37020    36626     -394     
==========================================
- Hits        28133    28047      -86     
+ Misses       8887     8579     -308     

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[melanieclarke]

LGTM. Thanks for tidying up!