Merge pull request #39396 from Arhell/zh-upd

[zh] Update ConfigMap data extraction to use jsonpath instead of grep…

content/zh-cn/docs/reference/setup-tools/kubeadm/kubeadm-join.md

@@ -475,7 +475,7 @@ it off regardless. Doing so will disable the ability to use the `--discovery-tok
 * 从 API 服务器获取 `cluster-info` 文件：
 
 ```shell
-kubectl -n kube-public get cm cluster-info -o yaml | grep "kubeconfig:" -A11 | grep "apiVersion" -A10 | sed "s/    //" | tee cluster-info.yaml
+kubectl -n kube-public get cm cluster-info -o jsonpath='{.data.kubeconfig}' | tee cluster-info.yaml
 ```
 
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