Bug 21029: Make "Suspend until:" translatable

Bug 21029: Make "Suspend until:" translatable

The label was part of the holds.js file. As .js files are never
translatable it needs to be moved to template level.

Test plan:
- Place a hold on an item
- Go to the patron account
- Click on the Suspend button on the holds tab
- View the modal, the label before the date field "Suspend until:" is
now translatable.

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>