Bug 32814: Fix cataloguing/value_builder/callnumber-KU.pl

Bug 32814: Fix cataloguing/value_builder/callnumber-KU.pl

Use event parameter

This is part of the refactoring happening in bug 30975

Test plan:
1. Verify that the plugin continues to work as before

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit a925b07f7b5c182f2c8050886d58e08ce065eff3)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit bb388991ac8c46cdd785b98706606e2b7fcebde3)

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
(cherry picked from commit 64f03c5217bf6139a065b1e88386fc1a872beec8)
Signed-off-by: Arthur Suzuki <arthur.suzuki@biblibre.com>