chore: remove schema 4 feature flag and temp reprocess citations batch job

[nayib-jose-gloria]

Reason for Change

• Remove Schema 4 Feature Flags [post-migration] #6072

Changes

• remove schema 4 feature flag usages
• removed schema 4 feature flag from tests, FeatureFlagService
• update FeatureFlagService tests
• remove temp reprocess citations batch job

Testing steps

• automated tests

Checklist 🛎️

Notes for Reviewer

[github-actions]

Deployment Summary

• backend_url: https://pr-6369-backend.rdev.single-cell.czi.technology
• frontend_url: https://pr-6369-frontend.rdev.single-cell.czi.technology
• delete_db_task_definition_arn: arn:aws:ecs:us-west-2:***:task-definition/dp-rdev-pr-6369-deletion:1
• migrate_db_task_definition_arn: arn:aws:ecs:us-west-2:***:task-definition/dp-rdev-pr-6369-migration:1

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (6e44c58) 91.99% compared to head (9dc45b4) 92.01%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6369      +/-   ##
==========================================
+ Coverage   91.99%   92.01%   +0.01%     
==========================================
  Files         180      180              
  Lines       14803    14789      -14     
==========================================
- Hits        13618    13608      -10     
+ Misses       1185     1181       -4     

Flag	Coverage Δ
unittests	92.01% <100.00%> (+0.01%)	⬆️

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[github-actions]

This PR has not seen any activity in the past 2 weeks; if nobody comments or reviews it in the next 3 days, this PR will be closed.

[danieljhegeman]

@nayib-jose-gloria @Bento007 are we sure we want to remove this?

[danieljhegeman]

I thought when we were quarterbacking this at least one of you was a strong proponent of building this solution in to keep around. @Bento007 don't you have a slice of code you were working on to do some aspect of the reprocessing? Can't remember where you ended up on that...

[nayib-jose-gloria]

@Bento007 made a point that keeping this around while we're not using it or working on productionalizing it just creates extra AWS job defs every time we create an rdev. Should we want to pick it up again and make it robust, it'd require enough of a rewrite that this code wouldn't be super useful anyway (most of the useful stuff is copied from the dataset metadata update batch job, so it is captured there should we want to expand that)

[danieljhegeman]

Approving though consider whether or not the reprocessing batch job should actually be removed, as commented on