update schema in vega_test.py

Author: clarasb

chartlets.py/tests/components/charts/vega_test.py

@@ -36,7 +36,7 @@ def test_with_chart_prop(self):
                 "id": "plot",
                 "theme": "dark",
                 "chart": {
-                    "$schema": "https://vega.github.io/schema/vega-lite/v5.20.1.json",
+                    "$schema": "https://vega.github.io/schema/vega-lite/v6.1.0.json",
                     "config": {
                         "view": {"continuousHeight": 300, "continuousWidth": 300}
                     },