Admin can't open Email / Logs

[msbt]

When trying to check the mail logs in Email -> Log, the superadmin-user works, regular admin throws this error and forwards to the dashboard:
Failed to fetch mail eventlogs. Object { name: "ClientError", statusCode: 403, status: "Forbidden", message: "role 'owner' is required but user has only 'admin'" }

Not sure if this is by design, if it is, we should rather hide the button to avoid confusion.

[girish]

@msbt It's intentional that only superadmins can see it. It won't be good for privacy if an admin could see all the emails being sent. It's OK for superadmins to see this because it's assumed they have SSH access.

I have added a note in https://docs.cloudron.io/email/#event-log and fixed the UI to hide the button for non-superadmins.