Remove units from the ref files

[WilliamJamieson]

Resolves RAD-nnnn

Closes #489

This PR removes the units from the reference files.

Tasks

• Update or add relevant rad tests.
• Update relevant docstrings and / or docs/ page.
• Does this PR change any schema files?
  • Schema changes were discussed at RAD Review Board meeting.
• 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 (https://github.com/spacetelescope/RegressionTests/actions/workflows/romancal.yml) with this branch installed ("git+https://github.com/<fork>/rad@<branch>").
  • Update relevant roman_datamodels utilities and tests.

News fragment change types:

• changes/<PR#>.feature.rst: new feature
• changes/<PR#>.bugfix.rst: fixes an issue
• changes/<PR#>.doc.rst: documentation change
• changes/<PR#>.removal.rst: deprecation or removal of public API
• changes/<PR#>.misc.rst: infrastructure or miscellaneous change

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.20%. Comparing base (810c17f) to head (a9a3080).
Report is 10 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #490      +/-   ##
==========================================
+ Coverage   95.81%   97.20%   +1.39%     
==========================================
  Files           4        4              
  Lines         215      215              
==========================================
+ Hits          206      209       +3     
+ Misses          9        6       -3     

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[schlafly]

Thanks. This looks good. We're currently storing the units as an optional, unused bit of the schema like this:
https://github.com/spacetelescope/rad/blob/main/src/rad/resources/schemas/wfi_image-1.0.0.yaml#L105
so at least the information is in principle present in a machine readable way. Would you mind adding those bits?

I think that doesn't actually affect RTB's ability to build the files, though, so we could advertise these branches to RTB and they could develop the needed files?