Update the create a cluster page

[nwneisen]

This was found as part of: https://mirantis.jira.com/browse/BOP-1223

The create cluster page has a few things that need to be updated

• The Example: A ready-to-deploy MKE configuration file is not ready-to-deploy. This is an outdated version of the config that is no longer valid. Some of the fields no longer exist. We should update this to be the current output of mkectl init or eliminate it altogether since we go on in the page to point users to mkectl init command which will always be the latest version
• The commands on the page tell users to name their config mke.yaml. We should change this to be the default config that is read by mkectl: mke4.yaml We should look for other config usage throughout the docs and do the same.
• We should move the first step of https://mirantis.github.io/mke-docs/docs/getting-started/create-cluster/#create-a-cluster so that it is a note that pops out rather than a step. It's not actually a part of the create a cluster process but it is definitely something that will cause someone issues if they don't notice it.