Remove unused niriss_bounding_box function from assign_wcs

[emolter]

Resolves JP-3970

This PR addresses removal of the unused niriss_bounding_box function from assign_wcs.

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]

starting regtests here https://github.com/spacetelescope/RegressionTests/actions/runs/14519057977

[melanieclarke]

I think @nden mentioned that we do not want to remove this - there are still some plans to use it for NIRISS.

[emolter]

Are you talking about #9256 (comment) ? That is not what I got from the discussion - I assumed the comment by @Rplesha would be relatively definitive w.r.t. whether this was desired. If that's wrong, I'm happy to close this PR as well as the GitHub issue, but let's figure out what's desired one way or the other.

[melanieclarke]

No, Nadia mentioned to me in an offline conversation that she still had plans for it, for WCS implementation purposes. It's possible I misunderstood, but hold off on this one until we hear from her, please.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.37%. Comparing base (233ff95) to head (9feff9e).
⚠️ Report is 889 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #9399   +/-   ##
=======================================
  Coverage   75.37%   75.37%           
=======================================
  Files         368      368           
  Lines       36885    36880    -5     
=======================================
- Hits        27802    27800    -2     
+ Misses       9083     9080    -3     

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[melanieclarke]

Closing in favor of #9456