Bug 25469: Typo: Item does not belongs to your library

Bug 25469: Typo: Item does not belongs to your library

This patch makes corrections to two strings in the batch delete template
to correct a typo. Before:

t("Item does not belongs to your library")

...after,

t("Item does not belong to your library")

To test, apply the patch and inspect the template to confirm that the
string is correct.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>