Do not bump kubernetes with dependabot
Without this patch, we'll get kubernetes updates. This is not necessary, and could be even a problem on merge: those kubernetes updates are done separately, knowingly, to respect the life cycle of the kubernetes we need (and stay one version below latest to have a larger coverage of versions). We could keep dependabot to update those on a lower frequency, but that sounds clunky and not great. Instead disable them all, and rely on the team to do this regular maintenance work.