Fix return type in doc of PyStructSequence_InitType2.

Author: bitdancer

Doc/c-api/tuple.rst

@@ -129,7 +129,7 @@ type.
    Initializes a struct sequence type *type* from *desc* in place.
 
 
-.. c:function:: void PyStructSequence_InitType2(PyTypeObject *type, PyStructSequence_Desc *desc)
+.. c:function:: int PyStructSequence_InitType2(PyTypeObject *type, PyStructSequence_Desc *desc)
 
    The same as ``PyStructSequence_InitType``, but returns ``0`` on success and ``-1`` on
    failure.