No-op backfill identifier_external_ids on vulnerability_reads

What does this MR do and why?

No-op the migration to queue BBM to backfill vulnerability_reads.identifier_external_ids with identifier.external_id data.

We do not require this migration and the removal steps were verified and confirmed with Database team in !160594 (diffs).

This is the First MR to cleanup involving the step:

• In Release N, No-op the contents of the #up and #down methods of the original migration file.

Related to #460080 (closed)

Database

> bundle exec rake db:migrate:up:main VERSION=20240627151711

main: == [advisory_lock_connection] object_id: 127720, pg_backend_pid: 23948
main: == [advisory_lock_connection] object_id: 127720, pg_backend_pid: 23948

> bundle exec rake db:migrate:down:main VERSION=20240627151711

main: == [advisory_lock_connection] object_id: 127720, pg_backend_pid: 24441
main: == 20240627151711 QueueBackfillIdentifierExternalIdsOfVulnerabilityReads: reverting
main: == 20240627151711 QueueBackfillIdentifierExternalIdsOfVulnerabilityReads: reverted (0.0033s)

main: == [advisory_lock_connection] object_id: 127720, pg_backend_pid: 24441

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