Allocate some unowned workers to categories

AdminEmailWorker only send repository check emails, so it belongs to
source code management. (It also doesn't run on GitLab.com.)

GitlabUsagePingWorker belongs to the collection category.

PruneOldEventsWorker relates to events which are used on the user
profile, so I've gone with users. This could also go under audit events,
potentially.

AdminEmailsWorker sends an admin-defined email to all users, so I put it
under issue tracking as that currently owns notifications (!). (This
also doesn't run on GitLab.com.)

app/workers/admin_email_worker.rb

@@ -7,7 +7,7 @@ class AdminEmailWorker
   include CronjobQueue
   # rubocop:enable Scalability/CronWorkerContext
 
-  feature_category_not_owned!
+  feature_category :source_code_management
 
   def perform
     send_repository_check_mail if Gitlab::CurrentSettings.repository_checks_enabled

app/workers/all_queues.yml

@@ -58,7 +58,7 @@
   :resource_boundary: :unknown
   :weight: 1
 - :name: cronjob:admin_email
-  :feature_category: :not_owned
+  :feature_category: :source_code_management
   :has_external_dependencies: 
   :latency_sensitive: 
   :resource_boundary: :unknown
@@ -88,7 +88,7 @@
   :resource_boundary: :unknown
   :weight: 1
 - :name: cronjob:gitlab_usage_ping
-  :feature_category: :not_owned
+  :feature_category: :collection
   :has_external_dependencies: 
   :latency_sensitive: 
   :resource_boundary: :unknown
@@ -142,7 +142,7 @@
   :resource_boundary: :cpu
   :weight: 1
 - :name: cronjob:prune_old_events
-  :feature_category: :not_owned
+  :feature_category: :users
   :has_external_dependencies: 
   :latency_sensitive: 
   :resource_boundary: :unknown

app/workers/gitlab_usage_ping_worker.rb

@@ -9,7 +9,7 @@ class GitlabUsagePingWorker
   include CronjobQueue
   # rubocop:enable Scalability/CronWorkerContext
 
-  feature_category_not_owned!
+  feature_category :collection
 
   # Retry for up to approximately three hours then give up.
   sidekiq_options retry: 10, dead: false

app/workers/prune_old_events_worker.rb

@@ -7,7 +7,7 @@ class PruneOldEventsWorker
   include CronjobQueue
   # rubocop:enable Scalability/CronWorkerContext
 
-  feature_category_not_owned!
+  feature_category :users
 
   DELETE_LIMIT = 10_000
 

ee/app/workers/admin_emails_worker.rb

@@ -3,7 +3,7 @@
 class AdminEmailsWorker
   include ApplicationWorker
 
-  feature_category_not_owned!
+  feature_category :issue_tracking
 
   # rubocop: disable CodeReuse/ActiveRecord
   def perform(recipient_id, subject, body)

ee/app/workers/all_queues.yml

@@ -364,7 +364,7 @@
   :resource_boundary: :unknown
   :weight: 1
 - :name: admin_emails
-  :feature_category: :not_owned
+  :feature_category: :issue_tracking
   :has_external_dependencies: 
   :latency_sensitive: 
   :resource_boundary: :unknown