Remove units from MOS pipeline.

[mairanteodoro]

Resolves RCAL-911

Closes #

This PR addresses ...

Tasks

• [ ] request a review from someone specific, to avoid making the maintainers review every PR
• [ ] add a build milestone, i.e. 24Q4_B15 (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 below for change types)
  • [ ] 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

news fragment change types...

• changes/<PR#>.general.rst: infrastructure or miscellaneous change
• changes/<PR#>.docs.rst
• changes/<PR#>.stpipe.rst
• changes/<PR#>.associations.rst
• changes/<PR#>.scripts.rst
• changes/<PR#>.mosaic_pipeline.rst
• changes/<PR#>.patch_match.rst

steps

• changes/<PR#>.dq_init.rst
• changes/<PR#>.saturation.rst
• changes/<PR#>.refpix.rst
• changes/<PR#>.linearity.rst
• changes/<PR#>.dark_current.rst
• changes/<PR#>.jump_detection.rst
• changes/<PR#>.ramp_fitting.rst
• changes/<PR#>.assign_wcs.rst
• changes/<PR#>.flatfield.rst
• changes/<PR#>.photom.rst
• changes/<PR#>.flux.rst
• changes/<PR#>.source_detection.rst
• changes/<PR#>.tweakreg.rst
• changes/<PR#>.skymatch.rst
• changes/<PR#>.outlier_detection.rst
• changes/<PR#>.resample.rst
• changes/<PR#>.source_catalog.rst