Bug 21939: Fix permissions for holds history tab

Bug 21939: Fix permissions for holds history tab

The tab will show when the staff user has edit_borrowers
permission, but the page itself will not be accessible.
This patch fixes the page permissions to allow access
with the edit_borrowers permission as suggested by the
comments on the original bug report.

To test:
- Create a staff user with only "edit_borrowers" permission
  from the borrowers module
- Try to access the holds history tab from any patron account
- Verify you are blocked
- Apply patch
- Try again and verify the page is accessible now
- Repeat with superlibrarian and full borrowers permission.

Signed-off-by: Séverine QUEUNE <severine.queune@bulac.fr>
Signed-off-by: Bob Bennhoff <bbennhoff@clicweb.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>