Merge branch '9837-link-for-external-alerts-goes-to-wrong-documentation' into 'master'

Resolve "Link for external alerts goes to wrong documentation"

Closes #9837

See merge request gitlab-org/gitlab-ee!9607

ee/app/views/projects/services/prometheus/_external_alerts.html.haml

@@ -3,6 +3,6 @@
 
 - notify_url = notify_project_prometheus_alerts_url(@project, format: :json)
 - authorization_key = @project.alerting_setting.try(:token)
-- learn_more_url = help_page_path('administration/monitoring/prometheus/index', anchor: 'configuring-prometheus')
+- learn_more_url = help_page_path('user/project/integrations/prometheus', anchor: 'external-prometheus-instances')
 
 #js-settings-prometheus-alerts{ data: { notify_url: notify_url, authorization_key: authorization_key, change_key_url: reset_alerting_token_project_settings_operations_path(@project), learn_more_url: learn_more_url } }