Add missing import

Author: EmandM

com.unity.netcode.gameobjects/TestHelpers/Runtime/NetcodeIntegrationTestHelpers.cs

@@ -2,6 +2,7 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
+using System.Net;
 using NUnit.Framework;
 using Unity.Netcode.Transports.UTP;
 using UnityEngine;