Update extensible-admission-controllers.md

update link

content/en/docs/reference/access-authn-authz/extensible-admission-controllers.md

@@ -57,7 +57,7 @@ In the following, we describe how to quickly experiment with admission webhooks.
 ### Write an admission webhook server
 
 Please refer to the implementation of the [admission webhook
-server](https://github.com/kubernetes/kubernetes/blob/v1.13.0/test/images/webhook/main.go)
+server](https://github.com/kubernetes/kubernetes/blob/master/test/images/agnhost/webhook/main.go)
 that is validated in a Kubernetes e2e test. The webhook handles the
 `AdmissionReview` request sent by the apiservers, and sends back its decision
 as an `AdmissionReview` object in the same version it received.
@@ -67,7 +67,7 @@ See the [webhook request](#request) section for details on the data sent to webh
 See the [webhook response](#response) section for the data expected from webhooks.
 
 The example admission webhook server leaves the `ClientAuth` field
-[empty](https://github.com/kubernetes/kubernetes/blob/v1.13.0/test/images/webhook/config.go#L47-L48),
+[empty](https://github.com/kubernetes/kubernetes/blob/master/test/images/agnhost/webhook/config.go#L39),
 which defaults to `NoClientCert`. This means that the webhook server does not
 authenticate the identity of the clients, supposedly apiservers. If you need
 mutual TLS or other ways to authenticate the clients, see