quick: Fix ownership of the floating view

Not nice to delete it in two places.

src/private/quick/FloatingWindowQuick.cpp

@@ -58,7 +58,8 @@ FloatingWindowQuick::FloatingWindowQuick(Frame *frame, MainWindowBase *parent)
 
 FloatingWindowQuick::~FloatingWindowQuick()
 {
-    m_quickWindow->deleteLater();
+    QWidgetAdapter::setParent(nullptr);
+    delete m_quickWindow;
 }
 
 QWindow *FloatingWindowQuick::candidateParentWindow() const

tests/utils.h

@@ -61,14 +61,6 @@ struct EnsureTopLevelsDeleted
 
     ~EnsureTopLevelsDeleted()
     {
-#ifdef KDDOCKWIDGETS_QTQUICK
-        // Delete the QQuickView. Too much assle to create and delete them for each test.
-        for (QWindow *window : qApp->topLevelWindows()) {
-            if (qobject_cast<QQuickView*>(window))
-                delete window;
-        }
-#endif
-
         if (topLevels().size() != 0) {
             qWarning() << "There's still top-level widgets present!" << topLevels();
         }