Automatic merge from submit-queue

Remove archived clientset

We have [client-go](https://github.com/kubernetes/client-go) now, no need to keep archived clientset in master of k8s.io/kubernetes.

Also updated the client-gen README.

Fix https://github.com/kubernetes/kubernetes/issues/35803.

cc @mikedanese 

```release-note
The main kubernetes repository stops hosting archived version of released clients. Please use [client-go](https://github.com/kubernetes/client-go).
```