Some cleanups to folly::EventBase after converting to folly::Function
Summary:[Folly] Some cleanups to `folly::EventBase` after converting to `folly::Function`.
* Fix up some comments referring to `std::function`.
* Remove the `SmallFunctor` bits - `folly::Function` takes over for that.
* Remove `runFunctionPtr` - it's unused.
Reviewed By: spacedentist
Differential Revision:
D3155511
fb-gh-sync-id:
38c75d1254993f59c8eaa7826dc8d9facb50a3a1
fbshipit-source-id:
38c75d1254993f59c8eaa7826dc8d9facb50a3a1