Remove unused usings

Author: jcansdale

src/GitHub.VisualStudio.16/CompositionServices.cs

@@ -8,11 +8,9 @@
 using System.Linq;
 using System.Reflection;
 using GitHub.Api;
-using GitHub.Factories;
 using GitHub.Services;
 using GitHub.Settings;
 using GitHub.VisualStudio.Settings;
-using GitHub.VisualStudio.Views;
 using GitHub.VisualStudio.Views.Dialog.Clone;
 using Microsoft.VisualStudio.Shell;
 using Microsoft.VisualStudio.Threading;