[FIX] website: no text-primary in accordion snippet
[FIX] website: no text-primary in accordion snippet

For some unknown reasons, the text-primary class was added on each
card-header of that snippet... while the default link color is already
primary by default.

This was however breaking some themes whose primary color would not fit
in card-header while the link color (different from the primary one)
would.

closes odoo/odoo#28627
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo