Summary:
- Replace a wordy type alias in `Future-inl.h` to use `remove_cvref_t`.
Pull Request resolved: https://github.com/facebook/folly/pull/1099

Differential Revision: D14721023

Pulled By: yfeldblum

fbshipit-source-id: e9de76a851162163046dfa088a8cc7e5a075562c