parsers: correctly decref normed value after PyDict_SetItem

Previously we were leaving this PyObject* with a refcount that was one
too high. Detected with cpychecker.

mercurial/parsers.c

@@ -253,9 +253,12 b' static PyObject *make_file_foldmap(PyObj'
 
 			if (normed == NULL)
 				goto quit;
-			if (PyDict_SetItem(file_foldmap, normed, k) == -1)
+			if (PyDict_SetItem(file_foldmap, normed, k) == -1) {
+				Py_DECREF(normed);
 				goto quit;
 		}
+			Py_DECREF(normed);
+		}
 	}
 	return file_foldmap;
 quit: