fix zh doc: default cpu example namespace

Author: houko

content/zh-cn/docs/tasks/administer-cluster/manage-resources/cpu-default-namespace.md

@@ -292,7 +292,7 @@ kubectl delete namespace default-cpu-example
 删除你的命名空间：
 
 ```shell
-kubectl delete namespace constraints-cpu-example
+kubectl delete namespace default-cpu-example
 ```
 
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