Bug 35245: Set default width for select2 in authorities

Bug 35245: Set default width for select2 in authorities

Test plan:
1) Edit a authority Marc framework, e.g. 'CHRON_TERM', visit:
   /cgi-bin/koha/admin/auth_tag_structure.pl?authtypecode=CHRON_TERM
2) Pick any field to turn into a AV field, e.g. 371, and edit its subfields:
   /cgi-bin/koha/admin/auth_subfields_structure.pl?tagfield=371&authtypecode=CHRON_TERM
3) Pick a subfield e.g. 'd' and click edit, visit:
   /cgi-bin/koha/admin/auth_subfields_structure.pl?op=add_form&tagfield=371&tagsubfield=d&authtypecode=CHRON_TERM#subdfield
4) Pick a Authorized value list e.g. DEPARTMENT, click Submit
5) Create a new authority of the same type 'CHRON_TERM', visit:
   /cgi-bin/koha/authorities/authorities.pl?authtypecode=CHRON_TERM
6) Click on Tab '3' and click on field 371 ADDRESS to expand it
7) Notice field 'd' select2 width is very narrow
8) Apply patch. Repeat. Notice its not narrow anymore

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit f918c3ff803d811ad025bff42e1263e3b3aafa83)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>