Merge branch 'ab/allow-change-column-null' into 'master'

Allow change_column_null in lock retries helper

See merge request gitlab-org/gitlab!39611

db/migrate/20200811055018_remove_not_null_constraint_on_type_from_audit_events.rb

@@ -7,7 +7,6 @@ class RemoveNotNullConstraintOnTypeFromAuditEvents < ActiveRecord::Migration[6.0
 
   disable_ddl_transaction!
 
-  # rubocop:disable Migration/WithLockRetriesDisallowedMethod
   # To avoid deadlock on audit_event and audit_event_part... since there is a trigger to insert record from audit_events
   # to audit_events_part..., we need to ensure each ALTER TABLE command run in its own transaction.
   def up
@@ -19,7 +18,6 @@ class RemoveNotNullConstraintOnTypeFromAuditEvents < ActiveRecord::Migration[6.0
       change_column_null :audit_events, :type, true
     end
   end
-  # rubocop:enable Migration/WithLockRetriesDisallowedMethod
 
   def down
     # no-op -- null values might be added after this constraint is removed.

rubocop/cop/migration/with_lock_retries_disallowed_method.rb

@@ -18,6 +18,7 @@ module RuboCop
           remove_column
           execute
           change_column_default
+          change_column_null
           remove_foreign_key_if_exists
           remove_foreign_key_without_error
           table_exists?