[zh-cn]Fix delete extra words“上”

[zh-cn]Fix delete extra words“上”

Author: javadoors

content/zh-cn/docs/tasks/administer-cluster/kubeadm/kubeadm-certs.md

@@ -532,7 +532,7 @@ to expiration a new set of CSRs for the serving certificates will be created and
 be approved to complete the rotation. To understand more see
 [Certificate Rotation](/docs/reference/access-authn-authz/kubelet-tls-bootstrapping/#certificate-rotation).
 -->
-默认情况下，这些服务证书上会在一年后过期。
+默认情况下，这些服务证书会在一年后过期。
 kubeadm 将 `KubeletConfiguration` 的 `rotateCertificates` 字段设置为
 `true`；这意味着证书快要过期时，会生成一组针对服务证书的新的 CSR，而
 这些 CSR 也要被批准才能完成证书轮换。