Update access-cluster.md with a comment that for IPv6

the user should use [::1] for the localhost

Author: Robert Pothier

docs/tasks/access-application-cluster/access-cluster.md

@@ -55,7 +55,8 @@ $ kubectl proxy --port=8080 &
 
 See [kubectl proxy](/docs/user-guide/kubectl/{{page.version}}/#proxy) for more details.
 
-Then you can explore the API with curl, wget, or a browser, like so:
+Then you can explore the API with curl, wget, or a browser, replacing localhost
+with [::1] for IPv6, like so:
 
 ```shell
 $ curl http://localhost:8080/api/