Bug 27230: Display OPAC description for OPAC_SUG

Bug 27230: Display OPAC description for OPAC_SUG

The authorised values OPAC_SUG displayed at the OPAC show the staff
description.

Test plan:
1. Create an auth value in opac_sug, with different text for the description and OPAC description.
2. Go to the OPAC and open the purchase suggestion form.
3. Note in the Reason for purchase drop down, the descriptions appear, the text entered in the OPAC description field.

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit 7063f2c4763d7fec870a4c326837b8b64e64004f)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>