trivial: remove an extra colon at the end of uefi-dbx error
trivial: remove an extra colon at the end of uefi-dbx error

fwupd/fwupd,hughsie/fwupd,hughsie/fwupd,hughsie/fwupd,fwupd/fwupd,fwupd/fwupd,hughsie/fwupd,fwupd/fwupd