Update resource boundary for ExportCsvWorker

At the time of writing the last 15 days worth of this job spent more
than 50% of its time on CPU. This sets the boundary accordingly.

ee/app/workers/all_queues.yml

@@ -421,7 +421,7 @@
   :feature_category: :issue_tracking
   :has_external_dependencies: 
   :latency_sensitive: 
-  :resource_boundary: :memory
+  :resource_boundary: :cpu
   :weight: 1
 - :name: ldap_group_sync
   :feature_category: :authentication_and_authorization

ee/app/workers/export_csv_worker.rb

@@ -4,7 +4,7 @@ class ExportCsvWorker
   include ApplicationWorker
 
   feature_category :issue_tracking
-  worker_resource_boundary :memory
+  worker_resource_boundary :cpu
 
   def perform(current_user_id, project_id, params)
     @current_user = User.find(current_user_id)