update ulong to long/

Author: DeepakRajendranMsft

src/ResourceManager/Network/Commands.Network/Models/PSVirtualNetworkGatewayConnection.cs

@@ -38,9 +38,9 @@ public class PSVirtualNetworkGatewayConnection : PSTopLevelResource
 
         public string ConnectionStatus { get; set; }
 
-        public ulong EgressBytesTransferred { get; set; }
+        public long? EgressBytesTransferred { get; set; }
 
-        public ulong IngressBytesTransferred { get; set; }
+        public long? IngressBytesTransferred { get; set; }
 
         public List<PSTunnelConnectionHealth> TunnelConnectionStatus { get; set; }