fix checked state of window menu entries at startup (bug #39322) * file-editor-interface.h: remove connet_visibility_changed * file-editor.cc/.h: remove connect_visibility_changed and slot handle_visibility which are aleady implemented in octave-dock-widget * octave-dock-widget.cc(connect_visibility_changed): moved here from octave-dock-widget.h, emit signal active_change for initializing the entries of the window menu * octave-dock-widget.h: move connect_visibility_changed to *.cc,