[3.12] Fix the confusing "User-defined methods" reference in the datamodel (GH-114276) (#114365)

Author: miss-islington

Doc/reference/datamodel.rst

@@ -1524,7 +1524,7 @@ Class method objects
 A class method object, like a static method object, is a wrapper around another
 object that alters the way in which that object is retrieved from classes and
 class instances. The behaviour of class method objects upon such retrieval is
-described above, under "User-defined methods". Class method objects are created
+described above, under :ref:`"instance methods" <instance-methods>`. Class method objects are created
 by the built-in :func:`classmethod` constructor.