Adapt quickstart installation instructions
Adapt quickstart installation instructions

It seems that new environments need explicit installation of the
kubectl GKE integration.

Change-Id: Ifa0d7edf6d5649dc2251818a56969ad87f39662d
GitOrigin-RevId: 0a8a132099f1a3ea427fd7be5623e3af682453d4

googlecloudrobotics/core,googlecloudrobotics/core,googlecloudrobotics/core