Hide remove_nodes from the azcli - not supported

[ryanhamel]

azslurm is inheriting the remove_nodes action from scalelib's clilib, but it should not be supported in Slurm because we can not really safely remove a node from Slurm, like in other schedulers.

Note this command removes the node from the scheduler, but does not shut it down.
We may find a way to use this with dynamic nodes, however.