Unbreak timeline delegate in Qt6: re-enable hover events on viewport

Apparently the hover events are not emitted for Qt6 on a viewport
by default, so we have to explicitly opt-in to get this behavior.

src/models/timelinedelegate.cpp

@@ -146,6 +146,7 @@ TimeLineDelegate::TimeLineDelegate(FilterAndZoomStack* filterAndZoomStack, QAbst
  , m_view(view)
 {
  m_view->viewport()->installEventFilter(this);
+ m_view->viewport()->setAttribute(Qt::WA_Hover);
 
  connect(filterAndZoomStack, &FilterAndZoomStack::filterChanged, this, &TimeLineDelegate::updateView);
  connect(filterAndZoomStack, &FilterAndZoomStack::zoomChanged, this, &TimeLineDelegate::updateZoomState);