Clean-up a warning since express is defined to be greater than v4.16.0 by the package.json definition. (#437)

hello-world/app.js

@@ -4,11 +4,10 @@
 // ------------------------------------------------------------
 
 const express = require('express');
-const bodyParser = require('body-parser');
 require('isomorphic-fetch');
 
 const app = express();
-app.use(bodyParser.json());
+app.use(express.json());
 
 const daprPort = process.env.DAPR_HTTP_PORT || 3500;
 const stateStoreName = `statestore`;