Update comment based on suggestion.

Author: phungleson

src/libcore/task/wake.rs

@@ -190,8 +190,9 @@ impl LocalWaker {
 impl From<LocalWaker> for Waker {
     /// Converts a `LocalWaker` into a `Waker`.
     ///
-    /// This conversion forgets local waker and allocates a new waker with
-    /// the same inner.
+    /// This conversion turns a `!Sync` `LocalWaker` into a `Sync` `Waker`, allowing a wakeup
+    /// object to be sent to another thread, but giving up its ability to do specialized
+    /// thread-local wakeup behavior.
     #[inline]
     fn from(local_waker: LocalWaker) -> Self {
         local_waker.0