Make RepositoryUpdateRemoteMirrorWorker idempotent

The job can be run multiple times with the same params
without side effects.

app/workers/all_queues.yml

@@ -2021,7 +2021,7 @@
   :urgency: :low
   :resource_boundary: :unknown
   :weight: 1
-  :idempotent:
+  :idempotent: true
   :tags: []
 - :name: self_monitoring_project_create
   :feature_category: :metrics

app/workers/repository_update_remote_mirror_worker.rb

 # frozen_string_literal: true
 
-class RepositoryUpdateRemoteMirrorWorker # rubocop:disable Scalability/IdempotentWorker
+class RepositoryUpdateRemoteMirrorWorker
   UpdateError = Class.new(StandardError)
 
   include ApplicationWorker
@@ -11,6 +11,7 @@ class RepositoryUpdateRemoteMirrorWorker # rubocop:disable Scalability/Idempoten
   sidekiq_options retry: 3, dead: false
   feature_category :source_code_management
   loggable_arguments 1
+  idempotent!
 
   LOCK_WAIT_TIME = 30.seconds
   MAX_TRIES = 3

spec/workers/repository_update_remote_mirror_worker_spec.rb

@@ -3,9 +3,8 @@
 require 'spec_helper'
 
 RSpec.describe RepositoryUpdateRemoteMirrorWorker, :clean_gitlab_redis_shared_state do
-  subject { described_class.new }
+  let_it_be(:remote_mirror) { create(:remote_mirror) }
 
-  let(:remote_mirror) { create(:remote_mirror) }
   let(:scheduled_time) { Time.current - 5.minutes }
 
   around do |example|
@@ -19,6 +18,8 @@ RSpec.describe RepositoryUpdateRemoteMirrorWorker, :clean_gitlab_redis_shared_st
   end
 
   describe '#perform' do
+    subject { described_class.new }
+
     it 'calls out to the service to perform the update' do
       expect_mirror_service_to_return(remote_mirror, status: :success)
 
@@ -68,4 +69,8 @@ RSpec.describe RepositoryUpdateRemoteMirrorWorker, :clean_gitlab_redis_shared_st
       subject.perform(remote_mirror.id, scheduled_time)
     end
   end
+
+  include_examples 'an idempotent worker' do
+    let(:job_args) { [remote_mirror.id, scheduled_time] }
+  end
 end