Make migration a no-op

Since this migration is already deployed on some environments, we make
this a no-op so that it we don't have to cleanup the schema_migrations
table for consistency

db/migrate/20210507191949_add_remove_on_issue_close_to_labels.rb

+# frozen_string_literal: true
+
+class AddRemoveOnIssueCloseToLabels < ActiveRecord::Migration[6.0]
+  # This migration was reverted in https://gitlab.com/gitlab-org/gitlab/-/merge_requests/62056
+
+  def up
+  end
+
+  def down
+  end
+end

db/schema_migrations/20210507191949

+ab662ff92a4e2a7d324f0652da6f0725e1c38e387f08b89921b43816b5d35834
\ No newline at end of file