bpo-33649: Note that asyncio.run() calls shutdown_asyncgens() (GH-9380)

(cherry picked from commit ac94e38d076aebc56c2ff96a249b5e40f32633ea)

Co-authored-by: Yury Selivanov <yury@magic.io>
diff --git a/Doc/library/asyncio-eventloop.rst b/Doc/library/asyncio-eventloop.rst
index 3b13a81..2522242 100644
--- a/Doc/library/asyncio-eventloop.rst
+++ b/Doc/library/asyncio-eventloop.rst
@@ -152,8 +152,12 @@
    close with an :meth:`~agen.aclose()` call.  After calling this method,
    the event loop will issue a warning if a new asynchronous generator
    is iterated. This should be used to reliably finalize all scheduled
-   asynchronous generators, e.g.::
+   asynchronous generators.
 
+   Note that there is no need to call this function when
+   :func:`asyncio.run` is used.
+
+   Example::
 
     try:
         loop.run_forever()