bpo-34476: Document that asyncio.sleep() always suspends. (GH-9643) (#9654)

(cherry picked from commit cd602b8)

Co-authored-by: Hrvoje Nikšić <hniksic@gmail.com>

Author: 2 people

Doc/library/asyncio-task.rst

@@ -270,6 +270,9 @@ Sleeping
    If *result* is provided, it is returned to the caller
    when the coroutine completes.
 
+   ``sleep()`` always suspends the current task, allowing other tasks
+   to run.
+
    The *loop* argument is deprecated and scheduled for removal
    in Python 3.10.