Revert "Disable vsix check."

The underlying issue has been fixed, so we can renable this check.

src/VisualStudio/Core/Def/Implementation/Experimentation/AnalyzerVsixSuggestedActionCallback.cs

@@ -14,8 +14,7 @@
 
 namespace Microsoft.VisualStudio.LanguageServices.Implementation.Experimentation
 {
-    // Disabling until https://github.com/dotnet/roslyn/issues/19629 is fixed.
-    // [Export(typeof(ISuggestedActionCallback))]
+    [Export(typeof(ISuggestedActionCallback))]
     internal class AnalyzerVsixSuggestedActionCallback : ForegroundThreadAffinitizedObject, ISuggestedActionCallback
     {
         private const string AnalyzerEnabledFlight = @"LiveCA/LiveCAcf";
@@ -52,7 +51,6 @@ public void OnSuggestedActionExecuted(SuggestedAction action)
             // thread to get it
             AssertIsForeground();
 
-            
             // If the user has previously clicked don't show again, then we bail out immediately
             if (_workspace.Options.GetOption(AnalyzerABTestOptions.NeverShowAgain))
             {