Remove @deprecated features.

pkg/observe/lib/src/observable.dart

Index: pkg/observe/lib/src/observable.dart
diff --git a/pkg/observe/lib/src/observable.dart b/pkg/observe/lib/src/observable.dart
index ca9408589a2c4c655dd5c91641501965dc04d537..b5b390d5a4c03e802fde18c799e43bf5d66bbf94 100644
--- a/pkg/observe/lib/src/observable.dart
+++ b/pkg/observe/lib/src/observable.dart
@@ -171,21 +171,6 @@ abstract class Observable {
   }
 }
 
-/**
- * *Deprecated* use [Observable.notifyPropertyChange] instead.
- *
- * This API should not be used as it creates a
- * [PropertyChangeRecord] without oldValue and newValue.
- *
- * Notify the property change. Shorthand for:
- *
- *     target.notifyChange(new PropertyChangeRecord(target, name, null, null));
- */
-@deprecated
-void notifyProperty(Observable target, Symbol name) {
-  target.notifyChange(new PropertyChangeRecord(target, name, null, null));
-}
-
 // TODO(jmesserly): remove the instance method and make this top-level method
 // public instead?
 _notifyPropertyChange(Observable obj, Symbol field, Object oldValue,