bump stdatamodels to 1.8.4

[zacharyburnett]

This PR addresses new test-breaking datamodels updates

Checklist for maintainers

• added entry in CHANGES.rst within the relevant release section
• updated or added relevant tests
• updated relevant documentation
• added relevant milestone
• added relevant label(s)
• ran regression tests, post a link to the Jenkins job below.
  How to run regression tests on a PR
• Make sure the JIRA ticket is resolved properly

[zacharyburnett]

regtest succeeded at https://plwishmaster.stsci.edu:8081/blue/organizations/jenkins/RT%2FJWST/detail/JWST/2673/pipeline/193/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (c5a0371) 75.91% compared to head (ba95832) 75.94%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8105      +/-   ##
==========================================
+ Coverage   75.91%   75.94%   +0.02%     
==========================================
  Files         460      460              
  Lines       37625    37625              
==========================================
+ Hits        28564    28573       +9     
+ Misses       9061     9052       -9     

Flag	Coverage Δ		*Carryforward flag
nightly	77.37% <ø> (ø)		Carriedforward from c5a0371

*This pull request uses carry forward flags. Click here to find out more.

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