fix ActorScroller not updating actors

It could also wrap each actor in a frame, so actors can tween,
but that can wait until there's a need.

stepmania/src/ActorScroller.cpp

@@ -76,6 +76,8 @@ void ActorScroller::Update( float fDeltaTime )
 		fX = roundf( fX );
 		fY = roundf( fY );
 		m_vActors[i]->SetXY( fX, fY );
+
+		m_vActors[i]->Update( fDeltaTime );
 	}
 }