JoinHandle docs: add missing 'the'

Author: RalfJung

library/std/src/thread/mod.rs

@@ -1273,7 +1273,7 @@ impl<T> JoinInner<T> {
 /// An owned permission to join on a thread (block on its termination).
 ///
 /// A `JoinHandle` *detaches* the associated thread when it is dropped, which
-/// means that there is no longer any handle to thread and no way to `join`
+/// means that there is no longer any handle to the thread and no way to `join`
 /// on it.
 ///
 /// Due to platform restrictions, it is not possible to [`Clone`] this