Updates the workflow to build shell images to use newer Google actions and updates the image Dockerfile to get the kubectl command from the k8s.io repos. The latter is what fixes the broken build, well the former just gets rid of warnings and assures we're using stuff that's still maintained.
TL;DR
Shell image builds were failing and this fixes it
Details
Updates the workflow to build shell images to use newer Google actions and updates the image Dockerfile to get the
kubectlcommand from thek8s.iorepos. The latter is what fixes the broken build, well the former just gets rid of warnings and assures we're using stuff that's still maintained.