Update codeowners

[braingram]

Cleans up codeowners file.

Checklist

• Added entry in CHANGES.rst under the corresponding subsection
• updated relevant tests
• updated relevant documentation
• Passed romancal regression testing on Jenkins / PLWishMaster. Link: https://plwishmaster.stsci.edu:8081/job/RT/job/romancal/XXX/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.70%. Comparing base (087a60d) to head (8ef960d).
Report is 63 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #375      +/-   ##
==========================================
+ Coverage   97.56%   97.70%   +0.14%     
==========================================
  Files          30       37       +7     
  Lines        2788     3357     +569     
==========================================
+ Hits         2720     3280     +560     
- Misses         68       77       +9     

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[schlafly]

Thanks!