bpo-39973: Fix the docs for PyObject_GenericSetDict() (GH-19026)

PyObject_GenericSetDict() takes three arguments, not two.
(cherry picked from commit a45b695)

Co-authored-by: Zackery Spytz <[email protected]>

Author: miss-islington

Doc/c-api/object.rst

@@ -128,7 +128,7 @@ Object Protocol
    .. versionadded:: 3.3
 
 
-.. c:function:: int PyObject_GenericSetDict(PyObject *o, void *context)
+.. c:function:: int PyObject_GenericSetDict(PyObject *o, PyObject *value, void *context)
 
    A generic implementation for the setter of a ``__dict__`` descriptor. This
    implementation does not allow the dictionary to be deleted.

Doc/data/refcounts.dat

@@ -1655,7 +1655,8 @@ PyObject_GenericSetAttr:PyObject*:name:0:
 PyObject_GenericSetAttr:PyObject*:value:+1:
 
 PyObject_GenericSetDict:int:::
-PyObject_GenericSetDict:PyObject*:o:+1:
+PyObject_GenericSetDict:PyObject*:o:0:
+PyObject_GenericSetDict:PyObject*:value:+1:
 PyObject_GenericSetDict:void*:context::
 
 PyObject_GetAttr:PyObject*::+1: