fix a typo in Baton comments
fix a typo in Baton comments

Summary: While `wake()` is an accurate-enough description of what the function in question does, the actual name of the function is `post()`.

Reviewed By: luciang

Differential Revision: D31617933

fbshipit-source-id: b45f062dccada3cedab2e2b7e7734f6b0b501e63

facebook/folly,facebook/folly,facebook/folly,facebook/folly,facebook/folly