Hide the Manage Attendees button if it is not permitted for the user

[akirk]

Clicking on Manage Attendees for an event I didn't create but I can edit (I suppose because of Admin on the site)

gives me

[trymebytes]

The reason for this is because the edit_translation_event_attendees cap check is missing here. However, we introduced the edit_translation_event_attendees cap to fix #242 .
Since we introduced the edit_translation_event_title and other similar capabilities for form fields, I believe we no longer need the edit_translation_event_attendees cap and we can make use of the edit_translation_event cap check to check if a user can edit attendees.

Therefore if a user can access the edit form, they should be able to edit the event attendees.