[kwin] Mark unused variables as unused

--warnings

kcmkwin/kwinscreenedges/screenpreviewwidget.cpp

@@ -126,6 +126,7 @@ void ScreenPreviewWidget::resizeEvent(QResizeEvent *e)
 
 void ScreenPreviewWidget::paintEvent(QPaintEvent *event)
 {
+    Q_UNUSED(event)
     if (d->monitorRect.size().isEmpty()) {
         return;
     }

libkwineffects/kwinanimationeffect.cpp

@@ -842,6 +842,7 @@ region_creation:
 
 void AnimationEffect::_expandedGeometryChanged(KWin::EffectWindow *w, const QRect &old)
 {
+    Q_UNUSED(old)
     Q_D(AnimationEffect);
     AniMap::const_iterator entry = d->m_animations.constFind(w);
     if (entry != d->m_animations.constEnd()) {