Update docs on iree-opt to use a file and options that still exist.
Update docs on iree-opt to use a file and options that still exist.

google/iree,iree-org/iree,iree-org/iree,iree-org/iree,google/iree,google/iree,iree-org/iree,google/iree,iree-org/iree,google/iree,iree-org/iree,google/iree,iree-org/iree,google/iree