Merge branch '118788-automatic-metric-alerts-part-2' into 'master'

Automatic created Ngnix alert after Prometheus install (2/2)

Closes #118788

See merge request gitlab-org/gitlab!29291

app/services/prometheus/create_default_alerts_service.rb

@@ -16,6 +16,11 @@ module Prometheus
         identifier: 'response_metrics_nginx_ingress_http_error_rate',
         operator: 'gt',
         threshold: 0.1
+      },
+      {
+        identifier: 'response_metrics_nginx_http_error_percentage',
+        operator: 'gt',
+        threshold: 0.1
       }
     ].freeze