_pickle: Fix load_counted_tuple(), use Py_ssize_t for size

Fix a warning on Windows 64-bit.

Modules/_pickle.c

@@ -5056,7 +5056,7 @@ load_counted_binunicode(UnpicklerObject *self, int nbytes)
 }
 
 static int
-load_counted_tuple(UnpicklerObject *self, int len)
+load_counted_tuple(UnpicklerObject *self, Py_ssize_t len)
 {
     PyObject *tuple;