scheduled reminders: limit to group doesn't support smart groups

To reproduce, setup a scheduled reminder (I was using one that triggers x days before a membership end date) and in the limit to group option select a smart group that includes a contact that would meet the reminder criteria. Trigger the reminders – user does not receive the email.

This is because the limit to group option only joins with the group_contact table using the basic group membership model. It doesn't support smart group membership. As a result, contacts do not receive the reminder who are expected to.