InstalledPage: don't override sortOrder

This is a fix to it not being included in: !239

discover/qml/InstalledPage.qml

@@ -8,7 +8,6 @@ import org.kde.kirigami 2.14 as Kirigami
 ApplicationsListPage {
     id: page
     stateFilter: AbstractResource.Installed
-    sortOrder: Qt.AscendingOrder
     allBackends: true
     sortProperty: "installedPageSorting"
     sortRole: DiscoverSettings.installedPageSorting