fix specialized list from dict keys (#23267)
Summary:
Previously we weren't specializing the list returned from `dict.keys()`
Pull Request resolved: https://github.com/pytorch/pytorch/pull/23267
Differential Revision: D16448512
Pulled By: eellison
fbshipit-source-id: fcd2a37ac680bdf90219b099a94aa36a80f4067c
