RCAL-927: Add ref_file entry for reference pixel subtraction reference file

[PaulHuwe]

Resolves RCAL-927

Closes #

This PR adds ref_file entry for reference pixel subtraction reference file.

Tasks

• [ ] update or add relevant tests
• [ ] update relevant docstrings and / or docs/ page
• [ ] Does this PR change any API used downstream? (if not, label with no-changelog-entry-needed)
  • [ ] write news fragment(s) in changes/: echo "changed something" > changes/<PR#>.<changetype>.rst (see below for change types)
  • [ ] start a romancal regression test with this branch installed ("git+https://github.com/<fork>/roman_datamodels@<branch>")

news fragment change types...

- ``changes/.feature.rst``: new feature - ``changes/.bugfix.rst``: fixes an issue - ``changes/.doc.rst``: documentation change - ``changes/.removal.rst``: deprecation or removal of public API - ``changes/.misc.rst``: infrastructure or miscellaneous change

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 97.77%. Comparing base (087a60d) to head (0a679d9). Report is 55 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #397 +/- ## ========================================== + Coverage 97.56% 97.77% +0.21% ========================================== Files 30 36 +6 Lines 2788 3461 +673 ========================================== + Hits 2720 3384 +664 - Misses 68 77 +9 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[PaulHuwe]

Regression Tests: https://github.com/spacetelescope/RegressionTests/actions/runs/11208792665