Fix symbology bug with GeoJSON layers added by Python API (#1023)

Author: mfisher87

python/jupytergis_lab/jupytergis_lab/notebook/gis_document.py

@@ -304,6 +304,10 @@ def add_geojson_layer(
                 "source": source_id,
                 "color": color_expr,
                 "opacity": opacity,
+                "symbologyState": {
+                    "renderType": "Single Symbol",
+                    "mode": "equal interval",
+                },
             },
             "filters": {
                 "appliedFilters": [