remove unused Link<> field

Change-Id: I0ca782c355933da740920e0368ffddeb0dc413a9
Reviewed-on: https://gerrit.libreoffice.org/18777Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>

sd/source/ui/inc/taskpane/TaskPaneTreeNode.hxx

@@ -172,8 +172,6 @@ protected:
 
 private:
     TreeNode* mpParent;
-    typedef ::std::vector<Link<>> StateChangeListenerContainer;
-    StateChangeListenerContainer maStateChangeListeners;
 };
 
 /** Objects of this class are sent to listeners to notify them about state