Revert "Aggregation: Fix crash when components are in parent-child relationship"

This reverts commit 12428bf1d6 because it triggers a qassert
in QObject::setParent when the object is a widget.

Change-Id: Ib9b76192f548cd3201fcb78a19ea88ccb5782ba2
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/libs/aggregation/aggregate.cpp

@@ -193,9 +193,6 @@ void Aggregate::deleteSelf(QObject *obj)
         QWriteLocker locker(&lock());
         aggregateMap().remove(obj);
         m_components.removeAll(obj);
-        // Avoid issues if obj was child of another component of the aggregate.
-        // The parent is deleted in ~Aggregate and might still have a reference on obj
-        obj->setParent({});
     }
     delete this;
 }