Improve documentation on how to update to a new API version

[matthchr]

You need to use kubectl apply, not something like kubectl edit, to change the APIVersion of a resource.

If you try to use kubectl edit, it says:

k edit managedclusters samplemanagedcluster202221 
A copy of your changes has been stored to "/tmp/kubectl-edit-1724071947.yaml"
error: At least one of apiVersion, kind and name was changed