[FIX] website: fix menu button edition

The content of the button was not changed after editing a menu button.

Part of https://github.com/odoo/odoo/pull/70150


task-2513588

closes odoo/odoo#71177

X-original-commit: 727c39db1a28c6539044f230ceb70d80ca05b8de
Signed-off-by: Jérémy Kersten (jke) <jke@openerp.com>