Bug 32821: Fix cataloguing/value_builder/stocknumber.pl

Bug 32821: Fix cataloguing/value_builder/stocknumber.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 97c050eacb87cc78f8cdfc3a37d240372b164437)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit 475871b3a40dd77ddbd487da30e34cdad5deb6cf)

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
(cherry picked from commit cfb990f641557de9ed1656dd07fd071b6c464b52)
Signed-off-by: Arthur Suzuki <arthur.suzuki@biblibre.com>