Revert unneeded fixes in flat_hash_map (#16907)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16907
The begin()/end() fix actually doesn't make sense, see my comment on https://github.com/skarupke/flat_hash_map/pull/8
This diff removes it.
Reviewed By: ezyang
Differential Revision: D13985779
fbshipit-source-id: f08b02c941069e2a4e728e02a19b65dc72f96b41
