Fix ServiceDeskEmailReceiverWorker urgency

Worker metadata is not inherited when sub-classing, so this had default
urgency incorrectly when it should have been high urgency.

app/workers/all_queues.yml

@@ -2703,7 +2703,7 @@
   :worker_name: ServiceDeskEmailReceiverWorker
   :feature_category: :service_desk
   :has_external_dependencies:
-  :urgency: :low
+  :urgency: :high
   :resource_boundary: :unknown
   :weight: 1
   :idempotent:

app/workers/service_desk_email_receiver_worker.rb

@@ -6,6 +6,7 @@ class ServiceDeskEmailReceiverWorker < EmailReceiverWorker # rubocop:disable Sca
   data_consistency :always
 
   feature_category :service_desk
+  urgency :high
   sidekiq_options retry: 3
 
   # https://gitlab.com/gitlab-com/gl-infra/scalability/-/issues/1087#jobs-written-to-redis-without-passing-through-the-application