pythongh-112066: Fix versionadded in PyDict_SetDefaultRef docs (pytho…

…nGH-118696)

(cherry picked from commit 447edb6)

Co-authored-by: Lysandros Nikolaou <lisandrosnik@gmail.com>

Doc/c-api/dict.rst

@@ -191,6 +191,7 @@ Dictionary Objects
    to both *default_value* and *\*result* (if it's not ``NULL``).
    These may refer to the same object: in that case you hold two separate
    references to it.
+
    .. versionadded:: 3.13