[IMP] website_sale : improve domain for not set category in product from...

... frontend  and remove other demo data of public categories

Task: https://www.odoo.com/web#id=10157&view_type=form&model=project.task&menu_id=3942&action=327
Pad: https://pad.odoo.com/p/r.iglL5xnK0X4Afc2m