[XLA] [NFC] Remove redundant options from multihost_hlo_runner
[XLA] [NFC] Remove redundant options from multihost_hlo_runner

Whether SPMD is used is inferrable from number of partitions, having both
num_partitions and use_spmd specified is redundant.

An extra flag to skip hlo passes is also redundant, since
--xla_disbale_hlo_passes could be just used.
