Comment 15 for bug 2017999

Thanks for the review. I tested what happens if a debconf answer is provided that will be removed by the update:

```
$ printf "tzdata tzdata/Areas select Europe\ntzdata tzdata/Zones/Europe select Uzhgorod\n" | debconf-set-selections
$ DEBIAN_FRONTEND=noninteractive apt install ./tzdata_2023c-0ubuntu0.20.04.2_all.deb
[...]
Current default time zone: 'Europe/Amsterdam'
```

So it will select the first entry of that area instead. So we need to keep all debconf options. I'll prepare a new set of debdiffs.