[en] update en docs to use recommended labels

content/en/examples/service/networking/dual-stack-preferred-svc.yaml

@@ -3,11 +3,11 @@ kind: Service
 metadata:
   name: my-service
   labels:
-    app: MyApp
+    app.kubernetes.io/name: MyApp
 spec:
   ipFamilyPolicy: PreferDualStack
   selector:
-    app: MyApp
+    app.kubernetes.io/name: MyApp
   ports:
     - protocol: TCP
       port: 80