Qt4PM: Fix warning

Change-Id: I65b3e950a78821c8395e13c459e1e4ad3d348b18
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>

src/plugins/qt4projectmanager/qt4nodes.cpp

@@ -720,6 +720,7 @@ void Qt4PriFileNode::watchFolders(const QSet<QString> &folders)
 
 void Qt4PriFileNode::folderChanged(const QString &changedFolder)
 {
+    Q_UNUSED(changedFolder);
     scheduleUpdate();
 }