ProjectExplorer: Don't save defaults to settings

Writes less settings and makes it possible to change defaults in the
future.

Task-number: QTCREATORBUG-24762
Change-Id: I73873b3684827b4fe27cfa5ea2f62a76003f9750
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/plugins/classview/classviewnavigationwidgetfactory.cpp

@@ -75,7 +75,9 @@ static QString settingsPrefix(int position)
 
 //! Flat mode settings
 
-void NavigationWidgetFactory::saveSettings(QSettings *settings, int position, QWidget *widget)
+void NavigationWidgetFactory::saveSettings(Utils::QtcSettings *settings,
+                                           int position,
+                                           QWidget *widget)
 {
     auto pw = qobject_cast<NavigationWidget *>(widget);
     QTC_ASSERT(pw, return);