Sync creation of i_compliance_violations_for_export

⚠ Blocked until !131084 (merged) is merged and index has been created.

What does this MR do and why?

Sync creation of i_compliance_violations_for_export

This is step two of the index creation for i_compliance_violations_for_export.

As stated in the docs, this should result on a no-op on Gitlab.com since the actual index has already been created in a post-deployment migration (see screenshot).

• Refs: Add (async) index on target_project_id for MR v... (!131084 - merged) • Sam Figueroa • 16.4
• Refs: Export report from compliance violation report (#356791 - closed) • Sam Figueroa • 16.4 • On track

Local migration run output

main: == [advisory_lock_connection] object_id: 227260, pg_backend_pid: 57026
main: == 20230906215669 AddIndexToViolationsOnTargetProjIdSync: migrating ===========
main: -- transaction_open?()
main:    -> 0.0000s
main: -- view_exists?(:postgres_partitions)
main:    -> 0.1002s
main: -- index_exists?("merge_requests_compliance_violations", [:target_project_id, :id], {:name=>"i_compliance_violations_for_export", :algorithm=>:concurrently})
main:    -> 0.0039s
main: -- execute("SET statement_timeout TO 0")
main:    -> 0.0002s
main: -- add_index("merge_requests_compliance_violations", [:target_project_id, :id], {:name=>"i_compliance_violations_for_export", :algorithm=>:concurrently})
main:    -> 0.0060s
main: -- execute("RESET statement_timeout")
main:    -> 0.0002s
main: == 20230906215669 AddIndexToViolationsOnTargetProjIdSync: migrated (0.1307s) ==

main: == [advisory_lock_connection] object_id: 227260, pg_backend_pid: 57026
ci: == [advisory_lock_connection] object_id: 227520, pg_backend_pid: 57028
ci: == 20230906215669 AddIndexToViolationsOnTargetProjIdSync: migrating ===========
ci: -- transaction_open?()
ci:    -> 0.0000s
ci: -- view_exists?(:postgres_partitions)
ci:    -> 0.0005s
ci: -- index_exists?("merge_requests_compliance_violations", [:target_project_id, :id], {:name=>"i_compliance_violations_for_export", :algorithm=>:concurrently})
ci:    -> 0.0033s
ci: -- execute("SET statement_timeout TO 0")
ci:    -> 0.0002s
ci: -- add_index("merge_requests_compliance_violations", [:target_project_id, :id], {:name=>"i_compliance_violations_for_export", :algorithm=>:concurrently})
ci:    -> 0.0048s
ci: -- execute("RESET statement_timeout")
ci:    -> 0.0003s
ci: == 20230906215669 AddIndexToViolationsOnTargetProjIdSync: migrated (0.0235s) ==

ci: == [advisory_lock_connection] object_id: 227520, pg_backend_pid: 57028

Screenshots or screen recordings

How to set up and validate locally

1. Checkout this MR's branch
2. Run: rake db:migrate

MR acceptance checklist

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