Remove unused fields.

src/EditorFeatures/Core/Tagging/AsynchronousTaggerProvider.cs

@@ -16,8 +16,6 @@ internal abstract class AsynchronousTaggerProvider<TTag> :
     {
         private readonly ITaggerProvider _underlyingTagger;
 
-        public event EventHandler<SnapshotSpanEventArgs> TagsChanged;
-
         protected AsynchronousTaggerProvider(
             IAsynchronousOperationListener asyncListener,
             IForegroundNotificationService notificationService)

src/EditorFeatures/Core/Tagging/AsynchronousViewTaggerProvider.cs

@@ -17,8 +17,6 @@ internal abstract class AsynchronousViewTaggerProvider<TTag> :
     {
         private readonly IViewTaggerProvider _underlyingTagger;
 
-        public event EventHandler<SnapshotSpanEventArgs> TagsChanged;
-
         protected AsynchronousViewTaggerProvider(
             IAsynchronousOperationListener asyncListener,
             IForegroundNotificationService notificationService)