Remove op_registration_util.bzl and rely on shim (#10935)

https://github.com/pytorch/executorch/pull/10924

See sync issue:
https://fb.workplace.com/groups/osssupport/permalink/28500287159593195/

We want to use the one in the shim, so we can refer to fbsource/xplat/..
/op_registration.bzl.