Retiring worker by name in SpecCluster

When a cluster retires a worker, it assumes the keys of `self.workers` are addresses in the RPC call: https://github.com/dask/distributed/blob/383ea0326ae103b5d5e0b62ed9c3cb18510c5b9e/distributed/deploy/spec.py#L333
But by default the workers are constructed with names per https://github.com/dask/distributed/blob/383ea0326ae103b5d5e0b62ed9c3cb18510c5b9e/distributed/deploy/spec.py#L498 (integers even, by default)
It seems to me that L333 should instead call `self.scheduler_comm.retire_workers(names=list(to_close))`