use replicas to replace kubectl scale deployment.

Signed-off-by: Weiping Cai <weiping.cai@daocloud.io>

content/en/docs/reference/kubectl/docker-cli-to-kubectl.md

@@ -41,7 +41,7 @@ kubectl create deployment --image=nginx nginx-app --port=80
 deployment.apps/nginx-app created
 ```
 
-```
+```shell
 # add env to nginx-app
 kubectl set env deployment/nginx-app  DOMAIN=cluster
 ```