parsers: avoid leak of nonnset and otherpset

Py_BuildValue increments the refcount, rather than stealing the
reference, which I missed in code review.

mercurial/parsers.c

@@ -604,6 +604,8 b' static PyObject *nonnormalotherparentent'
 	result = Py_BuildValue("(OO)", nonnset, otherpset);
 	if (result == NULL)
 		goto bail;
+	Py_DECREF(nonnset);
+	Py_DECREF(otherpset);
 	return result;
 bail:
 	Py_XDECREF(nonnset);