Revert D30095246: [pytorch][PR] Enable ncclAvg for reductions
Test Plan: revert-hammer
Differential Revision:
D30095246 (https://github.com/pytorch/pytorch/commit/a749180e4ed0b1840e08fb0ce580091fe70d8901)
Original commit changeset: d3a3475345fa
fbshipit-source-id: 34b5100b925859461296cae5a717a70e5eca6af6
