fix json output

tutorials/02.deploy-models.ipynb

@@ -296,7 +296,8 @@
         "    data = np.array(json.loads(raw_data)['data'])\n",
         "    # make prediction\n",
         "    y_hat = model.predict(data)\n",
-        "    return json.dumps(y_hat.tolist())"
+        "    # you can return any data type as long as it is JSON-serializable\n",
+        "    return y_hat.tolist()"
       ]
     },
     {