Add "app: prometheus" label to deployment

Author: lv185028

manifests/prometheus-service.yaml

@@ -30,8 +30,10 @@ spec:
 ---
 apiVersion: v1
 kind: Deployment
-apiVersion: extensions/v1beta1
+apiVersion: apps/v1
 metadata:
+  labels:
+    app: prometheus
   name: prometheus
 spec:
   replicas: 1