QmlDesigner: remove unclear "clearItems" function

It calls reset this model which is destructing at this moment.
There is no need to delete the items because they are objects
with the model as the parent.

Change-Id: I32be59238ea174faf66ce62ae9cd3ab02812d283
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

src/plugins/qmldesigner/components/itemlibrary/itemlibrarysectionmodel.cpp

@@ -39,7 +39,6 @@ ItemLibrarySectionModel::ItemLibrarySectionModel(QObject *parent) :
 
 ItemLibrarySectionModel::~ItemLibrarySectionModel()
 {
-    clearItems();
 }
 
 int ItemLibrarySectionModel::rowCount(const QModelIndex &) const
@@ -73,12 +72,6 @@ QHash<int, QByteArray> ItemLibrarySectionModel::roleNames() const
     return m_roleNames;
 }
 
-void ItemLibrarySectionModel::clearItems()
-{
-    beginResetModel();
-    endResetModel();
-}
-
 void ItemLibrarySectionModel::addItem(ItemLibraryItem *element)
 {
     m_itemList.append(element);

src/plugins/qmldesigner/components/itemlibrary/itemlibrarysectionmodel.h

@@ -45,8 +45,6 @@ public:
     QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const override;
     QHash<int, QByteArray> roleNames() const override;
 
-    void clearItems();
-
     void addItem(ItemLibraryItem *item);
 
     const QList<ItemLibraryItem *> &items() const;