effects: Fix window highlighting in WindowHeap

Currently, windows are not highlighted as expected in the window view
effect if the keyboard focus belongs to another screen view.

In general, it makes more sense to apply "Window.window.activeFocusItem"
constraint only to heap.selected.

src/effects/private/qml/WindowHeapDelegate.qml

@@ -135,7 +135,7 @@ Item {
             imagePath: "widgets/viewitem"
             prefix: "hover"
             z: -1
-            visible: !thumb.windowHeap.dragActive && (hoverHandler.hovered || thumb.selected) && Window.window.activeFocusItem && windowHeap.effectiveOrganized
+            visible: !thumb.windowHeap.dragActive && (hoverHandler.hovered || (thumb.selected && Window.window.activeFocusItem)) && windowHeap.effectiveOrganized
         }
 
         MouseArea {