drop opencv direct dependency

[braingram]

opencv is not used directly in jwst.

The jump step does use opencv but only via stcal (which has opencv as a dependency).

This PR removes opencv as a direct dependency to jwst.

Regtests: https://github.com/spacetelescope/RegressionTests/actions/runs/17494168542
all pass and show opencv installed "via stcal":
https://github.com/spacetelescope/RegressionTests/actions/runs/17494168542/job/49690870643#step:17:80

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

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.57%. Comparing base (53e8b83) to head (b77c94d).
⚠️ Report is 208 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #9803   +/-   ##
=======================================
  Coverage   82.57%   82.57%           
=======================================
  Files         366      366           
  Lines       37295    37295           
=======================================
  Hits        30796    30796           
  Misses       6499     6499           

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