Clean up usings

Author: jcansdale

src/GitHub.VisualStudio/Commands/GoToSolutionOrPullRequestFileCommand.cs

@@ -7,7 +7,6 @@
 using Microsoft.VisualStudio.Shell;
 using Microsoft.VisualStudio.Editor;
 using Microsoft.VisualStudio.Shell.Interop;
-using Microsoft.VisualStudio.TextManager.Interop;
 using Microsoft.VisualStudio.Text.Editor;
 using Microsoft.VisualStudio.Text.Differencing;
 using Task = System.Threading.Tasks.Task;