Fixing CI issues

Author: mdupras

src/ImageSharp.Web.Providers.AWS/Caching/AWSS3StorageCacheOptions.cs

@@ -1,5 +1,6 @@
 // Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
+using System;
 
 namespace SixLabors.ImageSharp.Web.Caching.AWS
 {

src/ImageSharp.Web.Providers.AWS/IAWSS3BucketClientOptions.cs

@@ -1,6 +1,8 @@
 // Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
+using System;
+
 namespace SixLabors.ImageSharp.Web
 {
     /// <summary>

src/ImageSharp.Web.Providers.AWS/Providers/AWSS3StorageImageProviderOptions.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
+using System;
 using System.Collections.Generic;
 
 namespace SixLabors.ImageSharp.Web.Providers.AWS

tests/ImageSharp.Web.Tests/TestUtilities/TestConstants.cs

@@ -1,6 +1,8 @@
 // Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
+using System;
+
 namespace SixLabors.ImageSharp.Web.Tests.TestUtilities
 {
     public static class TestConstants