Update the type of the tp_free slot.

Doc/ext/typestruct.h

@@ -65,7 +65,7 @@ typedef struct _typeobject {
     initproc tp_init;
     allocfunc tp_alloc;
     newfunc tp_new;
-    destructor tp_free; /* Low-level free-memory routine */
+    freefunc tp_free; /* Low-level free-memory routine */
     inquiry tp_is_gc; /* For PyObject_IS_GC */
     PyObject *tp_bases;
     PyObject *tp_mro; /* method resolution order */