Remove index_deployments_on_project_id_and_status asynchronously

What does this MR do and why?

This is part of an epic to optimize the deployments table by removing unused indexes: &10185

This MR is an asynchronous removal migration for index_deployments_on_project_id_and_status. The sync index removal will be done in a follow-up MR.

The definition of this index is:

"index_deployments_on_project_id_and_status" btree (project_id, status)

This index has a usage rate of 3.2689692699094675, but this is a duplicate of index_deployments_on_project_id_and_status_and_created_at and should be okay to remove. For more details, please read the issue description: #403595 (closed)

Screenshots or screen recordings

Migration output

main: == [advisory_lock_connection] object_id: 223440, pg_backend_pid: 90701
main: == 20230704044541 PrepareRemovalIndexDeploymentsOnProjectIdAndStatus: migrating 
main: -- index_exists?(:deployments, [:project_id, :status], {:name=>"index_deployments_on_project_id_and_status"})
main:    -> 0.0937s
main: -- quote_column_name("index_deployments_on_project_id_and_status")
main:    -> 0.0000s
main: == 20230704044541 PrepareRemovalIndexDeploymentsOnProjectIdAndStatus: migrated (0.1095s)

How to set up and validate locally

N/A

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #403595 (closed)