Fix default NavigationPolygon source geometry group name

Fixes default NavigationPolygon source geometry group name.

scene/resources/navigation_polygon.h

@@ -94,7 +94,7 @@ public:
 	uint32_t parsed_collision_mask = 0xFFFFFFFF;
 
 	SourceGeometryMode source_geometry_mode = SOURCE_GEOMETRY_ROOT_NODE_CHILDREN;
-	StringName source_geometry_group_name = "navigation_polygon_source_group";
+	StringName source_geometry_group_name = "navigation_polygon_source_geometry_group";
 
 	void set_vertices(const Vector<Vector2> &p_vertices);
 	Vector<Vector2> get_vertices() const;