Fix the dtype for the group dq flags

[WilliamJamieson]

In this comment: #615 (comment) it was pointed out that the group dq flags are in fact unsigned 8 bit integers not unsigned 32 bit integers. This is confirmed by the ramp schema: https://github.com/spacetelescope/rad/blob/c063796494d7526840d9e3ca37cccff3fcc9ad43/latest/ramp.yaml#L47

This PR updates the groupdq flags to be uint8 instead of uint32 and adds tests to make sure the dq flags meet the type expectations of the schemas.

Tasks

• Update or add relevant roman_datamodels 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 (https://github.com/spacetelescope/RegressionTests/actions/workflows/romancal.yml) with this branch installed ("git+https://github.com/<fork>/rad@<branch>").

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 94.95%. Comparing base (087a60d) to head (f66bc5a).
⚠️ Report is 221 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #616      +/-   ##
==========================================
- Coverage   97.56%   94.95%   -2.61%     
==========================================
  Files          30       27       -3     
  Lines        2788     2695      -93     
==========================================
- Hits         2720     2559     -161     
- Misses         68      136      +68     

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