Fix code warning in test

Author: shana

src/UnitTests/GitHub.App/ViewModels/PullRequestCreationViewModelTests.cs

@@ -30,7 +30,7 @@ public async Task NullDescriptionBecomesEmptyBody()
         vm.PRTitle = title;
 
         await vm.CreatePullRequest.ExecuteAsync();
-        ms.Received().CreatePullRequest(repository, vm.PRTitle, String.Empty, vm.SourceBranch, vm.TargetBranch);
+        var unused = ms.Received().CreatePullRequest(repository, vm.PRTitle, String.Empty, vm.SourceBranch, vm.TargetBranch);
     }
 
 }