bpo-40975: [doc] Identify AsyncExitStack.enter_async_context()/aclose() as coroutine methods (GH-20870) (GH-26254)

(cherry picked from commit c054e8f78f53035e06d6dc58c423d76c8a5fa39a)

Co-authored-by: naglis <naglis@users.noreply.github.com>
diff --git a/Doc/library/contextlib.rst b/Doc/library/contextlib.rst
index b92f703..dd903ce 100644
--- a/Doc/library/contextlib.rst
+++ b/Doc/library/contextlib.rst
@@ -578,7 +578,7 @@
    The :meth:`close` method is not implemented, :meth:`aclose` must be used
    instead.
 
-   .. method:: enter_async_context(cm)
+   .. coroutinemethod:: enter_async_context(cm)
 
       Similar to :meth:`enter_context` but expects an asynchronous context
       manager.
@@ -592,7 +592,7 @@
 
       Similar to :meth:`callback` but expects a coroutine function.
 
-   .. method:: aclose()
+   .. coroutinemethod:: aclose()
 
       Similar to :meth:`close` but properly handles awaitables.