kstyle: use antialiasing on combobox items

kstyle/breezestyle.cpp

@@ -104,6 +104,7 @@ namespace BreezePrivate
         //* paint
         void paint( QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const override
         {
+            painter->setRenderHints( QPainter::Antialiasing );
             // if the app sets an item delegate that isn't the default, use its drawing...
             if( _proxy && _proxy->metaObject()->className() != QStringLiteral("QComboBoxDelegate") ) {
                 _proxy.data()->paint( painter, option, index );