PyTorch should always depend on `future` (#35057)
Summary:
Because `past` is used in `caffe2.python.core`
Pull Request resolved: https://github.com/pytorch/pytorch/pull/35057
Test Plan: CI
Differential Revision: D20547042
Pulled By: malfet
fbshipit-source-id: cad2123c7b88271fea37f21e616df551075383a8
