Optimize projects_with_alerts_service_enabled qery

by using batch counting

lib/gitlab/usage_data.rb

@@ -98,7 +98,7 @@ module Gitlab
             projects_imported_from_github: count(Project.where(import_type: 'github')),
             projects_with_repositories_enabled: count(ProjectFeature.where('repository_access_level > ?', ProjectFeature::DISABLED)),
             projects_with_error_tracking_enabled: count(::ErrorTracking::ProjectErrorTrackingSetting.where(enabled: true)),
-            projects_with_alerts_service_enabled: count(AlertsService.active, batch: false),
+            projects_with_alerts_service_enabled: count(AlertsService.active),
             protected_branches: count(ProtectedBranch),
             releases: count(Release),
             remote_mirrors: count(RemoteMirror),