Bug 12884: Get rid of redefined subroutine warnings in dateaccessioned.pl

Instead of removing all warnings, we should remove warnings about the
redefined subroutines.

Test plan:
- link the dateaccessioned plugin with one of your biblio field
- edit an item
- verify they are no warnings in the Koha log file.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>

cataloguing/value_builder/dateaccessioned.pl

@@ -17,8 +17,9 @@
 # with Koha; if not, write to the Free Software Foundation, Inc.,
 # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
-use strict;
-use warnings;
+use Modern::Perl;
+
+no warnings 'redefine';
 
 =head1