Bug 17010 [Follow-up] Canceling a hold awaiting pickup no longer alerts librarian...

Bug 17010 [Follow-up] Canceling a hold awaiting pickup no longer alerts librarian about next hold

This patch makes a minor change to the markup to make the button in the
confirmation dialog conform to the appearance of similar buttons.

To test, follow the original test plan for this bug and verify that the
"OK" button in the dialog looks correct.

Signed-off-by: Liz Rea <liz@catalyst.net.nz>
Signed-off-by: Katrin Fischer  <katrin.fischer@bsz-bw.de>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit 2e79c211db318969b7c9d5ff538dfd54ba1aaed2)
Signed-off-by: Frédéric Demians <f.demians@tamil.fr>
(cherry picked from commit d9006fd602a8ac472bd9ce38422d82e2b65dd7ec)
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>