Bug 19357: (bug 18260 follow-up) Remove non-relevant attributes

Bug 19357: (bug 18260 follow-up) Remove non-relevant attributes

When created, batch_record_modification.tt has been based on
batch_delete_records.tt
These attributes are not used in the template and not set in the pl
script.
Since bug 18260, biblio is a Koha::Biblio and calling a non-existent
method will raise an error.

This patch get rid of the following error:
batch_record_modification.pl: Template process failed: undef error - The
method itemnumbers is not covered by tests!

Test plan:
Modify bibliographic records with the "Batch record modification" tool.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>