Bug 20018: use Modern::Perl in offline_circ scripts

Bug 20018: use Modern::Perl in offline_circ scripts

Test Plan:
- Check that it now says 'use Modern::Perl' and not 'use trict; use
warnings;' in the follwing plugins perl scripts

enqueue_koc.pl
list.pl
process.pl
process_koc.pl
service.pl

Signed-off-by: Jon Knight <J.P.Knight@lboro.ac.uk>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>