Revert D23468286: [pytorch][PR] Optimize code path for adaptive_avg_pool2d when output size is (1, 1)
Test Plan: revert-hammer
Differential Revision:
D23468286 (https://github.com/pytorch/pytorch/commit/f8f35fddd4b2bd788953d6d6ccfadf690b73a3e8)
Original commit changeset: cc181f705fea
fbshipit-source-id: 3a1db0eef849e0c2f3c0c64040d2a8b799644fa3
