ProjectExplorer: Don't show context menu when it makes no sense

Task-number: QTCREATORBUG-17152
Change-Id: Ic67386bdfd6d6d79e8a15bc6394a22cb46305335
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/projectexplorer/projectwindow.h

@@ -56,7 +56,6 @@ public:
     ProjectWindow();
 
 private:
-    void contextMenuEvent(QContextMenuEvent *event) override;
     void setPanel(QWidget *panel);
 };