remove unsused namespace

Author: Tiago Brenck

4-WebApp-your-API/Client/Controllers/TodoListController.cs

@@ -1,6 +1,5 @@
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc;
-using Microsoft.Identity.Client;
 using Microsoft.Identity.Web.Client;
 using System.Threading.Tasks;
 using TodoListClient.Services;