setup_robot: use the default context.
setup_robot: use the default context.

This makes setup_robot.sh work on minikube clusters (or other clusters
with a non-standard context name) without needing to manually set the
KUBE_CONTEXT variable.

Change-Id: I34528dca77eb67f6b3d1c2daf3b29a98d3e0cfd1
GitOrigin-RevId: 7ad11440db2a141c19ae6e0f6de9a67aca4dc28f

googlecloudrobotics/core,googlecloudrobotics/core,googlecloudrobotics/core