Revert D31932215: [pytorch][PR] Don't #define NUM_THREADS
Test Plan: revert-hammer
Differential Revision:
D31932215 (https://github.com/pytorch/pytorch/commit/f70e8064f4e6266ab945bc24345c622dc7933d0e)
Original commit changeset: ccdf11e249fb
fbshipit-source-id: 4c330aebe9cfb483f02ceb1fdaf5c3b0f8fa6fa1
