Don't use projection buffer as content source.

`.cshtml` files have a projection buffer which is the contents of the generated C#. Don't use this as a content source for diff matching as it's completely different to the file in git.

Author: grokys

src/GitHub.InlineReviews/Tags/InlineCommentTagger.cs

@@ -265,7 +265,8 @@ async Task SessionChanged(IPullRequestSession session)
             if (snapshot == null) return;
 
             var repository = gitService.GetRepository(session.LocalRepository.LocalPath);
-            file = await session.GetFile(relativePath, !leftHandSide ? this : null);
+            var isContentSource = !leftHandSide && !(buffer is IProjectionBuffer);
+            file = await session.GetFile(relativePath, isContentSource ? this : null);
 
             if (file == null) return;