Fix/private products data

CHANGELOG:

### Fixed
- [#606](https://gitlab.com/coopdevs/odoo-somconnexio/-/merge_requests/606) Add private to True in private products

Related card: https://trello.com/c/kNivFzzs/944-la-t-conserva-trenca-lapi-del-cat%C3%A0leg

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Fix the products as private products. They can be requested from the public form, only can vi requested by telephone or email.