Update Doc/whatsnew/3.15.rst

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

Author: serhiy-storchaka

Doc/whatsnew/3.15.rst

@@ -394,7 +394,7 @@ Other language changes
   syntax warnings by module name.
   (Contributed by Serhiy Storchaka in :gh:`135801`.)
 
-* Allowed defining the *__dict__* and *__weakref__* :ref:`__slots__ <_slots>`
+* Allowed defining the *__dict__* and *__weakref__* :ref:`__slots__ <slots>`
   for any class.
   Allowed defining any *__slots__* for a class derived from :class:`type` or
   other :c:member:`"variable-length" built-in type <PyTypeObject.tp_itemsize>`