QbsProjectManager: Remove some unused code

Change-Id: I5e77f5daeb8d7200e333443b0912c5be6e3b9f81
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>

src/plugins/qbsprojectmanager/qbsprojectmanager.cpp

@@ -60,8 +60,7 @@ namespace QbsProjectManager {
 
 qbs::Settings *QbsManager::m_settings = 0;
 
-QbsManager::QbsManager(Internal::QbsProjectManagerPlugin *plugin) :
-    m_plugin(plugin),
+QbsManager::QbsManager() :
     m_defaultPropertyProvider(new DefaultPropertyProvider)
 {
     m_settings = new qbs::Settings(Core::ICore::userResourcePath());