Turn old completion on when async completion is active.

Author: N. Taylor Mullen

src/Microsoft.VisualStudio.Editor.Razor/RazorDirectiveCompletionProvider.cs

@@ -115,9 +115,9 @@ public override Task ProvideCompletionsAsync(CompletionContext context)
  private Task AddCompletionItems(CompletionContext context)
  {
  if (!_textBufferProvider.TryGetFromDocument(context.Document, out var textBuffer) ||
- !_dependencies.Value.AsyncCompletionBroker.IsCompletionSupported(textBuffer.ContentType))
+ _dependencies.Value.AsyncCompletionBroker.IsCompletionSupported(textBuffer.ContentType))
  {
- // Completion is not supported.
+ // Async completion is supported that code path will handle completion.
  return Task.CompletedTask;
  }