convert delete bitmap querybox to .ui

Change-Id: Ie789954555012f766e48f9605f84e0ca5b2bca6d
Reviewed-on: https://gerrit.libreoffice.org/6717
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>