Update ExpoCell contentItem position upon its parent change

Since the position of the contentItem depends on the position and scale
of the parent item, make sure to re-evaluate it when the parent changes.

BUG:495501

src/plugins/private/expolayout.cpp

@@ -100,8 +100,14 @@ void ExpoCell::setContentItem(QQuickItem *item)
         return;
     }
 
+    if (m_contentItem) {
+        disconnect(m_contentItem, &QQuickItem::parentChanged, this, &ExpoCell::updateContentItemGeometry);
+    }
+
     m_contentItem = item;
 
+    connect(m_contentItem, &QQuickItem::parentChanged, this, &ExpoCell::updateContentItemGeometry);
+
     if (m_contentItem) {
         m_contentItem->setVisible(isVisible());
     }