and drop unused GALLERYBROWSERTRAVEL_CURRENT value

Change-Id: Id91824cbe024d4b5109ee0755b518164837bc6a6
Reviewed-on: https://gerrit.libreoffice.org/33965Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>