convert unlink image querybox to .ui

Change-Id: I46458d497757162be283effb624a7c769aeb5354
Reviewed-on: https://gerrit.libreoffice.org/7200
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>