Remove public wxFileHistory::RefreshLabels()

Replace it with a private DoRefreshLabels() and call it ourselves from
SetMenuPathStyle() to make the class simpler (and less error-prone, as
it's now impossible to forget to call RefreshLabels() any more) to use.

samples/menu/menu.cpp

@@ -1403,8 +1403,6 @@ void MyFrame::OnFileHistoryStyleItem(wxCommandEvent& event)
         m_fileHistory->SetMenuPathStyle(wxFH_PATH_SHOW_ALWAYS);
         break;
     }
-
-    m_fileHistory->RefreshLabels();
 }
 #endif