Update Kubernetes proxy URLs

[ShawnZhong]

This is briefly mentioned in the comment of a previous issue #2913 (comment).

Kubernetes made an API change to the proxy URL, which brakes some links in this repository.

Proxy URLs used to have /proxy in the middle, but it is moved to the end (See https://kubernetes.io/docs/tasks/access-application-cluster/access-cluster/#manually-constructing-apiserver-proxy-urls)

The list of links that need to be changed can be found here

Here is a list of links follows to the newest API:

[joshfischer1108]

Thanks for the note @ShawnZhong. We will hopefully get it addressed soon!