Wayland: Support classical indicators too

The Indicator Window is top-level, but on Wayland that can't do,
as we have no way to position it. So parent it. The indicators
are now under the window being dragged, but that's no so bad, as it's
smi-transparent, so you still see the indicator.

src/FrameworkWidgetFactory.cpp

@@ -91,12 +91,6 @@ FloatingWindow *DefaultWidgetFactory::createFloatingWindow(Frame *frame, MainWin
 
 DropIndicatorOverlayInterface *DefaultWidgetFactory::createDropIndicatorOverlay(DropArea *dropArea) const
 {
-    if (isWayland() && s_dropIndicatorType == DropIndicatorType::Classic) {
-        qWarning() << Q_FUNC_INFO << "Classical indicators aren't supported on Wayland yet."
-                   << "Falling back to Segmented Indicators";
-        s_dropIndicatorType = DropIndicatorType::Segmented;
-    }
-
     switch (s_dropIndicatorType) {
     case DropIndicatorType::Classic:
         return new ClassicIndicators(dropArea);