Revert D28474880: Allow Future::then to return pre-extracted DataPtrs
Test Plan: revert-hammer
Differential Revision:
D28474880 (https://github.com/pytorch/pytorch/commit/a0ee299d92d9e17cff696ca8f887171b4971f484)
Original commit changeset: 91a0dde5e29d
fbshipit-source-id: fabf7b0bcbd41342553660a4d1e4bfc3d1dd2d41
