Update zookeeper.md

kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.

content/en/docs/tutorials/stateful-application/zookeeper.md

@@ -266,7 +266,7 @@ to read the data from another.
 The command below executes the `zkCli.sh` script to write `world` to the path `/hello` on the `zk-0` Pod in the ensemble.
 
 ```shell
-kubectl exec zk-0 zkCli.sh create /hello world
+kubectl exec zk-0 -- zkCli.sh create /hello world
 ```
 
 ```