A restaurant is already allowed to refuse to sell arbitrarily. They have the right to freedom of association, just like anybody else, with narrow exceptions when it's targeted at protected classes. And restaurants are already allowed to do all sorts of things may depart from the gospel of revenue maximization.

This is the sort of thing we expect to be taken care of by the free market. If signing up with a delivery service is truly in their interest and aligns with what they want their business to be, they mostly will. And if not, that's fine.