Remove role check for anthology creation

[camdendotlol]

Addresses and closes #461

Testing

Visit staging and perform the following steps twice: first as a regular student user (without the teacher or admin roles), and then as a user with the teacher role.

1. You should be able to see a "Create new anthology" link on the https://staging.covecollective.org/ homepage as soon as you log in
2. Create an anthology
3. Make sure another user can join it