add: Hide ldap input

It was normally done by the Framanav, but the input was also in a modal
and the nav wasn't able to react to the modal rendering.

See: https://framagit.org/framasoft/framanav/blob/d33f490d56b5dc7afbd940b0803bc23e9a9875d4/app/components/partials/Nav.vue#L342-346