Bug 23286: Improve style of hold confirmation modal

Bug 23286: Improve style of hold confirmation modal

This patch makes minor changes to the hold confirmation modal in the
check-in template and adds some additional style. The goal is to make
the information a little more readable.

To test, apply the patch and rebuild the staff client CSS
(https://wiki.koha-community.org/wiki/Working_with_SCSS_in_the_OPAC_and_staff_client).

Check in items with the following hold statuses:

 - On hold for a patron at your library
 - On hold for a patron at another library
 - On hold and already marked 'Waiting'

Confirm that the hold confirmation modal is clear and well-styled.

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Nadine Pierre <nadine.pierre@inLibro.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>