[SCSB-223] prune dependencies to ONLY explicitly imported packages

[zacharyburnett]

Resolves SCSB-223

used valimdep to find unimported dependencies and undepended imports

Tasks

• If you have a specific reviewer in mind, tag them.
• add a build milestone, i.e. Build 12.0 (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 changelog readme for instructions)
  • 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

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.02%. Comparing base (bbf1e5f) to head (971c6bc).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10013      +/-   ##
==========================================
- Coverage   85.98%   85.02%   -0.96%     
==========================================
  Files         368      366       -2     
  Lines       38457    38437      -20     
==========================================
- Hits        33066    32682     -384     
- Misses       5391     5755     +364     

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[zacharyburnett]

regtest running at https://github.com/spacetelescope/RegressionTests/actions/runs/21000769909