fix yaml error in .gitlab-ci

.gitlab-ci.yml

@@ -559,7 +559,7 @@ testinfra:
 prometheus-stack-alerts:
   stage: health-test
   variables:
-    # APP var is used in job specific rules (i.e. .grafana_rules)
+    # APP var is used in job specific rules (i.e. .prometheus_stack_rules)
     APP: "prometheus-stack"
   allow_failure: true
   script:
@@ -600,7 +600,7 @@ grafana-behave:
     - job: grafana-cert
   extends:
     - .behave
-    - .grafana_rules
+    - .prometheus_stack_rules
 
 nextcloud-behave:
   variables: