LDAP group sync using filter should be EEP, not EES

https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/2885 is behind the ldap_extras feature check right now, along with all the existing LDAP group sync logic, which is EES. We need to put the filter radio button and the filter sync logic behind an extra EEP check.

https://gitlab.com/gitlab-org/gitlab-ee/issues/3188 had the ~"EE Premium" label set, but this was overlooked.