Remove unused INotify interface

Signed-off-by: Chris Forbes <chrisf@ijw.co.nz>

OpenRA.Game/Traits/TraitsInterfaces.cs

@@ -85,7 +85,6 @@ namespace OpenRA.Traits
 	public interface IResolveOrder { void ResolveOrder(Actor self, Order order); }
 	public interface IValidateOrder { bool OrderValidation(OrderManager orderManager, World world, int clientId, Order order); }
 	public interface IOrderVoice { string VoicePhraseForOrder(Actor self, Order order); }
-	public interface INotify { void Play(Player p, string notification); }
 	public interface INotifyCreated { void Created(Actor self); }
 	public interface INotifyAddedToWorld { void AddedToWorld(Actor self); }
 	public interface INotifyRemovedFromWorld { void RemovedFromWorld(Actor self); }