Remove Project::dependsOn(), it's never called

I don't remember why I did leave it alone in the reafctoring some years
ago, but surely it serves no purpose.

Change-Id: Idf920faf3f8f7128cd410501f2c3748e100dfbfb
Reviewed-by: Tobias Hunger <tobias.hunger@nokia.com>

src/plugins/qmlprojectmanager/qmlproject.cpp

@@ -272,11 +272,6 @@ ProjectExplorer::IProjectManager *QmlProject::projectManager() const
     return m_manager;
 }
 
-QList<ProjectExplorer::Project *> QmlProject::dependsOn()
-{
-    return QList<Project *>();
-}
-
 QList<ProjectExplorer::BuildConfigWidget*> QmlProject::subConfigWidgets()
 {
     return QList<ProjectExplorer::BuildConfigWidget*>();