Bug 28689: Extra %s in alert message when saving an items

Bug 28689: Extra %s in alert message when saving an items

This patch removes an unnecessary %s in the text built to show when
there are errors in the cataloging add item form.

To reproduce, open the add item form in cataloging and click "Add item"
without filling in all mandatory fields. You should see an alert message
that contains, "- %s 1 mandatory fields empty (highlighted)"

To test, apply the patch and return to the add item form. Now when you
save an incomplete form the message should omit the %s:

- 1 mandatory fields empty (highlighted)

https://bugs.koha-community.org/show_bug.cgi?id=28690

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>