Enhancement: Add permission to delete link passwords when password is enforced

We've added the ability to allow deleting passwords on public links, even if the password is enforced.
Therefore, the user needs respective permission, granted by the server.
This feature is only possible on public links that have the viewer role.

https://github.com/owncloud/web/pull/9857
https://github.com/owncloud/web/pull/9866
https://github.com/owncloud/ocis/issues/7538
