Fix typo in CS notification example of the Object class

doc/classes/Object.xml

@@ -175,7 +175,7 @@
 				        print("Goodbye!")
 				[/gdscript]
 				[csharp]
-				public override void _Notification(long what)
+				public override void _Notification(int what)
 				{
 				    if (what == NotificationPredelete)
 				    {