Simplify the ``LastUpdatedOrderedDict`` example recipe (GH-13296)

diff --git a/Doc/library/collections.rst b/Doc/library/collections.rst
index 64de970..e0469c2 100644
--- a/Doc/library/collections.rst
+++ b/Doc/library/collections.rst
@@ -1141,7 +1141,7 @@
 
         def __setitem__(self, key, value):
             super().__setitem__(key, value)
-            super().move_to_end(key)
+            self.move_to_end(key)
 
 An :class:`OrderedDict` would also be useful for implementing
 variants of :func:`functools.lru_cache`::