Drop issues.issue_type column

What does this MR do and why?

The column was ignored in 16.2 and associated indexes were already dropped in .com

Drop column timeline

• Column was ignored: !125320 (merged) - %16.2
• Column was dropped: !127679 (merged) - #416949 (closed) %16.3
• Remove ignore column from Issue model - Remove IgnorableColumns module from Issue model (#416950 - closed) scheduled for %16.4

DB review

Migration output

UP

bin/rails db:migrate
main: == [advisory_lock_connection] object_id: 224220, pg_backend_pid: 82991
main: == 20230726201351 RemoveIssuesIssueTypeColumn: migrating ======================
main: -- remove_column(:issues, :issue_type)
main:    -> 0.0015s
main: == 20230726201351 RemoveIssuesIssueTypeColumn: migrated (0.0052s) =============

main: == [advisory_lock_connection] object_id: 224220, pg_backend_pid: 82991
ci: == [advisory_lock_connection] object_id: 224420, pg_backend_pid: 82993
ci: == 20230726201351 RemoveIssuesIssueTypeColumn: migrating ======================
ci: -- remove_column(:issues, :issue_type)
ci:    -> 0.0010s
ci: == 20230726201351 RemoveIssuesIssueTypeColumn: migrated (0.0098s) =============

ci: == [advisory_lock_connection] object_id: 224420, pg_backend_pid: 82993

DOWN

bin/rails db:rollback:main db:rollback:ci
main: == [advisory_lock_connection] object_id: 223940, pg_backend_pid: 82180
main: == 20230726201351 RemoveIssuesIssueTypeColumn: reverting ======================
main: -- add_column(:issues, :issue_type, :smallint, {:default=>0, :null=>false})
main:    -> 0.0042s
main: == 20230726201351 RemoveIssuesIssueTypeColumn: reverted (0.0071s) =============

main: == [advisory_lock_connection] object_id: 223940, pg_backend_pid: 82180
ci: == [advisory_lock_connection] object_id: 225120, pg_backend_pid: 82448
ci: == 20230726201351 RemoveIssuesIssueTypeColumn: reverting ======================
ci: -- add_column(:issues, :issue_type, :smallint, {:default=>0, :null=>false})
ci:    -> 0.0032s
ci: == 20230726201351 RemoveIssuesIssueTypeColumn: reverted (0.0155s) =============

ci: == [advisory_lock_connection] object_id: 225120, pg_backend_pid: 82448

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 #416949 (closed)