Demo compile fix

tutorials/pick_and_place/PickAndPlaceProject/Assets/DemoScripts/Demo.cs

 #if UNITY_EDITOR
 using Microsoft.CSharp;
-using RosMessageGeneration;
 using RosSharp;
 using RosSharp.Control;
 using RosSharp.Urdf.Editor;
 using System.Text;
 using UnityEditor;
 using UnityEngine;
+using Unity.Robotics.ROSTCPConnector;
+using Unity.Robotics.ROSTCPConnector.MessageGeneration;
 
 public class Demo : MonoBehaviour
 {