Remove ignore_column directive

ee/app/models/approval_merge_request_rule.rb

@@ -5,9 +5,6 @@ class ApprovalMergeRequestRule < ApplicationRecord
   include ApprovalRuleLike
   include UsageStatistics
-  include IgnorableColumns
-  ignore_column :code_owner, remove_with: '13.5', remove_after: '2020-10-22'
-
   scope :not_matching_pattern, -> (pattern) { code_owner.where.not(name: pattern) }
   scope :matching_pattern, -> (pattern) { code_owner.where(name: pattern) }