Update Doc/c-api/object.rst

Co-authored-by: Petr Viktorin <[email protected]>

Author: colesbury

Doc/c-api/object.rst

@@ -647,6 +647,7 @@ Object Protocol
    This is intended as a building block for managing weak references
    without the overhead of a Python :ref:`weak reference object <weakrefobjects>`.
 
+
    Typically, correct use of this function requires support from *obj*'s
    deallocator (:c:member:`~PyTypeObject.tp_dealloc`).
    For example, the following sketch could be adapted to implement a