bpo-34123: Fix missed documentation update for dict.popitem(). (GH-8292)

Doc/library/stdtypes.rst

@@ -4220,12 +4220,18 @@ pairs within braces, for example: ``{'jack': 4098, 'sjoerd': 4127}`` or ``{4098:
 
    .. method:: popitem()
 
-      Remove and return an arbitrary ``(key, value)`` pair from the dictionary.
+      Remove and return a ``(key, value)`` pair from the dictionary.
+      Pairs are returned in :abbr:`LIFO (last-in, first-out)` order.
 
       :meth:`popitem` is useful to destructively iterate over a dictionary, as
       often used in set algorithms.  If the dictionary is empty, calling
       :meth:`popitem` raises a :exc:`KeyError`.
 
+      .. versionchanged:: 3.7
+
+      LIFO order is now guaranteed. In prior versions, :meth:`popitem` would
+      return an arbitrary key/value pair.
+
    .. method:: setdefault(key[, default])
 
       If *key* is in the dictionary, return its value.  If not, insert *key*