remove install/removeEventFilter from QRollEffect

This class doesn't have an eventFilter method.

Change-Id: Ibd7b3b5b954dd2467c9b4dadd85d3613964d9f7c
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@digia.com>
Reviewed-by: Andreas Holzammer <andreas.holzammer@kdab.com>

src/widgets/widgets/qeffects.cpp

@@ -474,8 +474,6 @@ void QRollEffect::run(int time)
     show();
     setEnabled(false);
 
-    qApp->installEventFilter(this);
-
     showWidget = true;
     done = false;
     anim.start(1);
@@ -535,7 +533,6 @@ void QRollEffect::scroll()
     }
     if (done || !widget) {
         anim.stop();
-        qApp->removeEventFilter(this);
         if (widget) {
             if (!showWidget) {
 #ifdef Q_OS_WIN