Bug 16043 - Use Font Awesome icon in hold confirmation dialog

 Bug 16043 - Use Font Awesome icon in hold confirmation dialog

This patch fixes another instance in the checkin template where a Font
Awesome icon should be used instead of a background image.

To test, apply the patch and locate an item which is on hold for a
patron at your logged in library.

- Check in the item.
- Confirm the hold.
- Check in the item again.
  - You should get a "Hold found (item is already waiting)" message. The
    "Print and confirm" button in this dialog should have a Font Awesome
    icon.
  - Confirm that the print button still works correctly.

Followed test plan, works as expected.
Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Brendan A Gallagher <brendan@bywatersolutions.com>