Core: Use QList's initializer list contructor for output panes

More concise code.

Change-Id: I0c83a02de725648294e1b6b49669bdec0c47fafe
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/todo/todooutputpane.cpp

@@ -67,11 +67,7 @@ QWidget *TodoOutputPane::outputWidget(QWidget *parent)
 
 QList<QWidget*> TodoOutputPane::toolBarWidgets() const
 {
-    return QList<QWidget*>()
-        << m_spacer
-        << m_currentFileButton
-        << m_wholeProjectButton
-        << m_subProjectButton;
+    return { m_spacer, m_currentFileButton, m_wholeProjectButton, m_subProjectButton };
 }
 
 QString TodoOutputPane::displayName() const