Remove unused using statements

samples/CookieSample/Program.cs

@@ -1,6 +1,5 @@
 using System.IO;
 using Microsoft.AspNetCore.Hosting;
-using Microsoft.Extensions.Configuration;
 
 namespace CookieSample
 {

src/Microsoft.AspNetCore.Authentication/Events/EventResultState.cs

@@ -1,8 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-using System;
-
 namespace Microsoft.AspNetCore.Authentication
 {
     public enum EventResultState

src/Microsoft.AspNetCore.Authentication/Properties/Resources.Designer.cs

@@ -1,7 +1,6 @@
 // <auto-generated />
 namespace Microsoft.AspNetCore.Authentication
 {
-    using System.Globalization;
     using System.Reflection;
     using System.Resources;
 

src/Microsoft.AspNetCore.Authentication/SharedAuthenticationOptions.cs

@@ -1,9 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-
-using System;
-
 namespace Microsoft.AspNetCore.Authentication
 {
     public class SharedAuthenticationOptions

src/Microsoft.AspNetCore.Authentication/Win32.cs

@@ -3,7 +3,6 @@
 
 
 using System;
-using System.ComponentModel;
 using System.Runtime.InteropServices;
 
 namespace Microsoft.Win32