Update to swh.model 6.13 introducing ModelObjectType

Needed to fix e.g. swh-graph's generate_dataset.py script.

swh/dataset/test/test_orc.py

@@ -81,7 +81,7 @@ def test_export_origin_visit():
 
 
 def test_export_origin_visit_status():
-    obj_type = ModelObjectType.ORIGIN_VISITS_STATUS
+    obj_type = ModelObjectType.ORIGIN_VISIT_STATUS
     output = exporter({obj_type: TEST_OBJECTS[obj_type]})
     for obj in TEST_OBJECTS[obj_type]:
         assert (