[FIX] website_slides: hide slide download button if not available
[FIX] website_slides: hide slide download button if not available

Task #1923443

Purpose
=======

The slides on the website showed the 'download' button regardless of the value of the 'download_security' field.
If the value is 'none', meaning that the slides are never downloadable, the button should be hidden.

closes #29904

closes odoo/odoo#30051
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo