add todo comment for Qt 7

Task-number: QTBUG-94546
Change-Id: I86a40dcb2b6e33140c31acc450bcd47fa6ff3f2d
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

src/widgets/itemviews/qtreewidget.h

@@ -205,6 +205,8 @@ private:
     QTreeWidget *view;
     QTreeWidgetItemPrivate *d;
     QTreeWidgetItem *par;
+    // ### Qt7: Move children to d-pointer and replace QList by a suitable data structure.
+    //          to fix QTBUG-94546
     QList<QTreeWidgetItem*> children;
     Qt::ItemFlags itemFlags;
 };