Fix test

Author: shana

src/UnitTests/GitHub.Exports/VSServicesTests.cs

@@ -16,6 +16,7 @@ public void CallsCloneOnVsProvidedCloneService(bool recurseSubmodules, CloneOpti
             var provider = Substitute.For<IUIProvider>();
             var gitRepositoriesExt = Substitute.For<IGitRepositoriesExt>();
             provider.GetService(typeof(IGitRepositoriesExt)).Returns(gitRepositoriesExt);
+            provider.TryGetService(typeof(IGitRepositoriesExt)).Returns(gitRepositoriesExt);
             var vsServices = new VSServices(provider);
 
             vsServices.Clone("https://github.com/github/visualstudio", @"c:\fake\ghfvs", recurseSubmodules);