The current summary of the operation is obscure.
It refers to a token in the ring and the endpoint associated with it,
while the operation uses a host_id to identify a whole node.
Instead, clarify the summary to refer to a node in the cluster,
consistent with the description for the host_id parameter.
Also, describe the effect the call has on the data the removed node
logically owned.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>