[3.12] Fix indentation for contextlib.asynccontextmanager docs (GH-127333) (#130580)

Co-authored-by: Jelle Zijlstra <[email protected]>

Author: miss-islington

Doc/library/contextlib.rst

@@ -151,9 +151,9 @@ Functions and classes provided:
    created by :func:`asynccontextmanager` to meet the requirement that context
    managers support multiple invocations in order to be used as decorators.
 
-  .. versionchanged:: 3.10
-     Async context managers created with :func:`asynccontextmanager` can
-     be used as decorators.
+   .. versionchanged:: 3.10
+      Async context managers created with :func:`asynccontextmanager` can
+      be used as decorators.
 
 
 .. function:: closing(thing)