[FIX] doc: use new URI wkhtmltopdf releases
[FIX] doc: use new URI wkhtmltopdf releases

The old release of wkhtmltopdf are no longer published on the download page.
The developer explicitely asks to use the github link

cf: wkhtmltopdf/wkhtmltopdf#3524
    wkhtmltopdf/wkhtmltopdf#3521
    wkhtmltopdf/wkhtmltopdf#3518
    wkhtmltopdf/wkhtmltopdf#3508

Closes #18146

ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo