Bug 20459: Correct message for cancelling an article request

Bug 20459: Correct message for cancelling an article request

We should not ask for 'cancel this hold'. Remove corresponding TODO.

Fix qa warning on old bootstrap style:
    btn btn-mini => btn btn-default btn-xs
I removed above change, qa tool complaint is wrong (refers to staff, we
        are on opac)

Test plan:
Create an article request and cancel it on opac-user.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>