Restored a using directive that proved to be necessary.

In some cases, references to `System.IO.Compression` members are #ifdef'd and only needed when the OS_WINDOWS compiler directive is present.

src/Runner.Worker/ActionManager.cs

@@ -1,7 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
-using System.IO.Compression;
+using System.IO.Compression;     // required for OS_WINDOWS
 using System.Linq;
 using System.Net;
 using System.Net.Http;

src/Runner.Worker/DiagnosticLogManager.cs

@@ -5,7 +5,6 @@ using System.IO.Compression;
 using GitHub.DistributedTask.WebApi;
 using System.Linq;
 using System.Globalization;
-using System.Threading.Tasks;
 using Pipelines = GitHub.DistributedTask.Pipelines;
 using GitHub.Runner.Common;
 using GitHub.Runner.Sdk;

src/Test/L0/Worker/ActionManagerL0.cs

@@ -13,7 +13,11 @@ using GitHub.DistributedTask.WebApi;
 using GitHub.Runner.Sdk;
 using GitHub.Runner.Worker;
 using GitHub.Runner.Worker.Container;
-using GitHub.Services.Common;
+
+#if OS_WINDOWS
+using System.IO.Compression;
+#endif
+
 using Moq;
 using Moq.Protected;
 using Xunit;