Remove dollar!

Close https://github.com/AvaloniaUI/Avalonia/issues/1397

src/Avalonia.Base/Collections/AvaloniaDictionary.cs

@@ -117,7 +117,7 @@ namespace Avalonia.Collections
             _inner = new Dictionary<TKey, TValue>();
 
             PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("Count"));
-            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs($"Item[]"));
+            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("Item[]"));
             
 
             if (CollectionChanged != null)
@@ -222,4 +222,4 @@ namespace Avalonia.Collections
             }
         }
     }
-}
+}