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/coreplugin/inavigationwidgetfactory.cpp

@@ -156,7 +156,9 @@ QKeySequence INavigationWidgetFactory::activationSequence() const
 
     \sa INavigationWidgetFactory::restoreSettings()
 */
-void INavigationWidgetFactory::saveSettings(QSettings * /* settings */, int /* position */, QWidget * /* widget */)
+void INavigationWidgetFactory::saveSettings(Utils::QtcSettings * /* settings */,
+                                            int /* position */,
+                                            QWidget * /* widget */)
 {
 }