We're just using the latest version of the `lachlanevenson/k8s-kubectl` container image. But, 5 days ago, a version was released for K8s 1.13 that doesn't appear to be able to apply our yamls onto OCP 4.

So, we should pin this to a a kubectl 1.12.x release.

Marking as a blocker as this breaks installing Knative from our knative-operators repo completely.