Bug 28579: Typo: No record have been imported because they all match an existing...

Bug 28579: Typo: No record have been imported because they all match an existing record in your catalog.

This patch corrects a grammatical error in text which might be shown
when adding records from a staged file to a basket. It corrects this:

  "No record have been imported because they all match an existing
  record in your catalog."

..to this:

  "No records have been imported because they all match existing
  records in your catalog."

To see the error in Koha, apply the patch and export some records from
Koha (Tools -> Export) and then re-import them using Tools -> Stage MARC
for import.

- Go to Acquisitions -> Vendor -> Basket -> Add to basket -> From a
  staged file.
- Click the "Add to order" button corresponding to the file you just
  uploaded.
- Select all records and define default accounting details.
- When you click "Save" you should see the error message.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Joonas Kylmälä <joonas.kylmala@iki.fi>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>