Issue yuriatgoogle#3: prometheus-demo.yaml uses obsolete apiVersion

Upped apiVersion to apps/v1 and added spec.selector section. File now loads and works on Kubernetes 1.17.

Signed-off-by: Rob Thorne <[email protected]>

kubernetes/prometheus-deployment.yaml

@@ -1,10 +1,13 @@
-apiVersion: extensions/v1beta1
+apiVersion: apps/v1
 kind: Deployment
 metadata:
   name: prometheus-deployment
   namespace: prometheus
 spec:
   replicas: 1
+  selector:
+    matchLabels:
+      app: prometheus-server
   template:
     metadata:
       labels:
@@ -30,4 +33,4 @@ spec:
             name: prometheus-server-conf
 
         - name: prometheus-storage-volume
-          emptyDir: {}
+          emptyDir: {}