Remove ElasticIndexerWorker in major release [RUN AS-IF-FOSS]

What does this MR do?

Related to #221178 (closed)

Note: I don't think this requires a changelog but happy to add one if it's required!

ElasticIndexerWorker was introduced in fe605235 and we stopped using it due to architectural changes introduced in: !33384 (merged)

Since this is a major release, we are cleaning up the unused worker per the Sidekiq styleguide

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

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