Notify Observers if Element changed with Index[] (dotnet#4598)

Are there any downsides to this? I needed to make this adjustment so that I could properly bind to elements in the Dictionary.

csharp/parallel/ParallelExtensionsExtras/CoordinationDataStructures/ObservableConcurrentDictionary.cs

@@ -50,6 +50,7 @@ private void NotifyObserversOfChange()
             {
                 collectionHandler?.Invoke(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
                 propertyHandler?.Invoke(this, new PropertyChangedEventArgs("Count"));
+                propertyHandler?.Invoke(this, new PropertyChangedEventArgs("Item[]"));
                 propertyHandler?.Invoke(this, new PropertyChangedEventArgs(nameof(Keys)));
                 propertyHandler?.Invoke(this, new PropertyChangedEventArgs(nameof(Values)));
             }, null);