QFileSystemModel::sort(): emit layoutChanged with VerticalSortHint

It's good to give a hint about what changed, and it helps behavior of
QQmlDelegateModel when that is used in the view.

Pick-to: 6.8
Fixes: QTBUG-131487
Change-Id: I8478eaf1e8294e101f3fedc285e44f83e600c566
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

src/gui/itemmodels/qfilesystemmodel.cpp

@@ -1178,7 +1178,7 @@ void QFileSystemModel::sort(int column, Qt::SortOrder order)
         newList.append(d->index(node, col));
 
     changePersistentIndexList(oldList, newList);
-    emit layoutChanged();
+    emit layoutChanged({}, VerticalSortHint);
 }
 
 /*!