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

folly/synchronization/Baton.h

@@ -317,7 +317,7 @@ class Baton {
       // state_ is the truth even if FUTEX_WAIT reported a matching
       // FUTEX_WAKE, since we aren't using type-stable storage and we
       // don't guarantee reuse.  The scenario goes like this: thread
-      // A's last touch of a Baton is a call to wake(), which stores
+      // A's last touch of a Baton is a call to post(), which stores
       // LATE_DELIVERY and gets an unlucky context switch before delivering
       // the corresponding futexWake.  Thread B sees LATE_DELIVERY
       // without consuming a futex event, because it calls futexWait