Update install runner on Kubernetes install page - docs

What does this MR do?

This merge request reorders the Kubernetes runner install docs page so that the installation step is logically positioned right after the pre-requisites section.

Why was this MR needed?

The rationale behind this change is that it is unclear the critical steps required and the order of operations to install and get a runner working on a Kubernetes cluster.

In the example from this blog post, its very clear what the user has to do to get the runner installed.