Fixed README in slack-infra
Fixed README in slack-infra

There was a mistake in `kubectl` name and also suggested command to
apply the resources was missing the `-R` flag to deploy resources
recursively

Signed-off-by: Bart Smykla <05a61b7a17440ad59b313e4d55e2ded5a86010f0@vmware.com>

thockin/k8s.io,kubernetes/k8s.io,thockin/k8s.io,kubernetes/k8s.io,kubernetes/k8s.io,thockin/k8s.io,kubernetes/k8s.io,thockin/k8s.io