Revert D24698027: Fix auto exponent issue for torch.pow
Test Plan: revert-hammer
Differential Revision:
D24698027 (https://github.com/pytorch/pytorch/commit/8ef7ccd669a36f49eb052d12a71df9b7836cafa5)
Original commit changeset: f23fdb65c925
fbshipit-source-id: 9a67a2c6310c9e4fdefbb421a8cd4fa41595bc9a
