Bugfix: Show timezone location in `snapshots` output

Since restic 0.19.0, the `snapshots` command printed the current timezone when
listing snapshots. However, the timezone can change during the year, for example,
due to daylight saving time. Instead just print the name of the current location.

https://github.com/restic/restic/pull/21876
https://forum.restic.net/t/possible-bug-in-timezone-naming/10867