Update library/std/src/sync/rwlock.rs

Co-authored-by: Steven Fackler <sfackler@gmail.com>

library/std/src/sync/rwlock.rs

@@ -24,7 +24,7 @@
 /// The priority policy of the lock is dependent on the underlying operating
 /// system's implementation, and this type does not guarantee that any
 /// particular policy will be used. In particular, a writer which is waiting to
-/// acquire the lock  in `write` might or might not block future calls to
+/// acquire the lock in `write` might or might not block concurrent calls to
 /// `read`.
 ///
 /// The type parameter `T` represents the data that this lock protects. It is