Bug 12612: Remove CGI::scrolling_list from auth_tag_structure.pl

Bug 12612: Remove CGI::scrolling_list from auth_tag_structure.pl

This patch removes the only instance in this file.

Don't know if the feature is of some utility, seems
that does not work (no use of auth values as indicators
on MARC authority editor)

To test:
1. Apply the patch
2. Go to Administration > Authority types
3. Clic on MARC structure of any fw
4. Clic Edit on any tag
5. On tag editor check the pulldown 'Authorised value', that was replaced
6. Check for regressions: select a value, save, verify the value, change
again, etc.

Note: removed a SELECT, using now C4::Koha::GetAuthorisedValueCategories

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Works as expected, no regressions found.

Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>