Revert D22467871: add check for duplicated op registration in JIT
Test Plan: revert-hammer
Differential Revision:
D22467871 (https://github.com/pytorch/pytorch/commit/a548c6b18ff5a337b6329ed7b2381cfb4d3da2ed)
Original commit changeset: 9b7a40a217e6
fbshipit-source-id: b594d4d0a079f7e24ef0efb45476ded2838cbef1
