Cleanup code related to approvers API update

Since the API endpoints have been deprecated
and removed, we can clean up the code that they
used

ee/app/services/concerns/cleanup_approvers.rb

-# frozen_string_literal: true
-
-# Concern that encapsulates logic to remove all
-# approvers in a project that were not added during
-# the current transaction
-module CleanupApprovers
-  extend ActiveSupport::Concern
-
-  private
-
-  # rubocop: disable CodeReuse/ActiveRecord
-  def cleanup_approvers(target, reload: false)
-    target.approvers.where.not(user_id: params[:approver_ids]).destroy_all # rubocop: disable Cop/DestroyAll
-    target.approver_groups.where.not(group_id: params[:approver_group_ids]).destroy_all # rubocop: disable Cop/DestroyAll
-
-    # If the target already has `approvers` and/or `approver_groups` loaded then we need to
-    # force a reload in order to not return stale information after the destroys above
-    if reload
-      target.approvers.reset
-      target.approver_groups.reset
-    end
-
-    target
-  end
-  # rubocop: enable CodeReuse/ActiveRecord
-end

ee/app/services/ee/merge_requests/update_service.rb

@@ -5,12 +5,9 @@ module EE
     module UpdateService
       extend ::Gitlab::Utils::Override
 
-      include CleanupApprovers
-
       override :execute
       def execute(merge_request)
         unless update_task_event?
-          should_remove_old_approvers = params.delete(:remove_old_approvers)
           old_approvers = merge_request.overall_approvers(exclude_code_owners: true)
         end
 
@@ -18,8 +15,6 @@ module EE
 
         merge_request = super(merge_request)
 
-        cleanup_approvers(merge_request, reload: true) if should_remove_old_approvers && merge_request.valid?
-
         merge_request.reset_approval_cache!
 
         return merge_request if update_task_event?

ee/app/services/ee/projects/update_service.rb

@@ -4,7 +4,6 @@ module EE
   module Projects
     module UpdateService
       extend ::Gitlab::Utils::Override
-      include CleanupApprovers
 
       PULL_MIRROR_ATTRIBUTES = %i[
         mirror
@@ -19,7 +18,6 @@ module EE
 
       override :execute
       def execute
-        should_remove_old_approvers = params.delete(:remove_old_approvers)
         limit = params.delete(:repository_size_limit)
         wiki_was_enabled = project.wiki_enabled?
 
@@ -33,7 +31,6 @@ module EE
         end
 
         if result[:status] == :success
-          cleanup_approvers(project) if should_remove_old_approvers
           refresh_merge_trains(project)
 
           log_audit_events