Current behavior that needs to be fixed: If an event has already ended and a user goes to /wiki/Special:RegisterForEvent/{id} there is still a submit button. The user can not successfully register, but the submit button still shows as if they would be allowed to register.

Priority: After V0 work, since this is not the primary way someone would register or unregister for an event

Acceptance Criteria:

• Hide 'submit' button if the event has ended (on special page for register and unregister)