remove test code for the Graph gadget

src/demo-1-config.js

@@ -22,15 +22,6 @@ export const flexlayout_json = {
             "type": "tab",
             "component": "int-trace",
           },
-          {
-            "name": "The magic graph",
-            "type": "tab",
-            "component": "graph",
-            "config": {
-              "hasReadme": true,
-              "topic": "/graph_dot",
-            }
-          },
         ]
       },
       {