[I18N] add auth_ldap module to .tx/config

The “Authentication via LDAP” module is not available on Transifex for
Odoo 16+ projects. This commit adds it to the list of translatable
resources by referencing it in .tx/config.

closes odoo/odoo#128431

Signed-off-by: Louis Wicket (wil) <wil@odoo.com>