asyncio: Fix docs for default event loop (GH-14308)


When the Windows default event loop changed, `asyncio-policy.rst` was updated but `asyncio-eventloop.rst` was missed.
(cherry picked from commit 9ffca670ed4df42eb256e7144619a9d3a830e7c0)

Co-authored-by: Ben Darnell <ben@bendarnell.com>
diff --git a/Doc/library/asyncio-eventloop.rst b/Doc/library/asyncio-eventloop.rst
index 8673f84..f763fd5 100644
--- a/Doc/library/asyncio-eventloop.rst
+++ b/Doc/library/asyncio-eventloop.rst
@@ -1454,7 +1454,7 @@
 :class:`SelectorEventLoop` and :class:`ProactorEventLoop`.
 
 By default asyncio is configured to use :class:`SelectorEventLoop`
-on all platforms.
+on Unix and :class:`ProactorEventLoop` on Windows.
 
 
 .. class:: SelectorEventLoop