GRUB_HIDDEN_TIMEOUT still referred to in postinst scripts despite change to GRUB_TIMEOUT_STYLE=hidden

[Mathieu Trudel-Lapierre]

We've moved to using GRUB_TIMEOUT_STYLE=hidden in /etc/default/grub, but debian/postinst.in still references GRUB_HIDDEN_TIMEOUT variable and attempts to set that in conffile handling:

    case @PACKAGE@ in
      grub-pc)
        apply_conf_tweaks "$conf_files" merge_debconf_into_conf GRUB_TIMEOUT grub-pc/timeout
        apply_conf_tweaks "$conf_files" sed_conf 's/^(GRUB_TIMEOUT=)"([0-9][0-9]*)"/\1\2/'
        db_get grub-pc/hidden_timeout
        if [ "$RET" = false ]; then
          apply_conf_tweaks "$conf_files" sed_conf 's/^GRUB_HIDDEN_TIMEOUT=/#&/'
        fi
      ;;

This may lead to confusion in grub's conffile handling and in the resulting /etc/default/grub, potentially leading to unnecessary debconf/ucf prompts for conffile changes.