I guess, at the moment there is no way to unenroll. Enrolling to a learning path with help you display the courses available in learning path. You can always choose to study one course n the learning patch and then go to catalogue and study another course. So Learning path is a group of few courses to help learners follow the stream they are intrested in. Catalogue lists all the course and learners are free to choose any course irrespective of enrolling in a different learning path.