Temporarily reduce DNS TTL for snowflake.torproject.net

Please set the DNS TTL for snowflake.torproject.net to something short, around 60 seconds.

Next week (24–28 January 2022) we plan to do a staged upgrade of the snowflake bridge: tpo/anti-censorship/pluggable-transports/snowflake#40095 (closed). We plan to set up a staging bridge to handle client traffic while we do the upgrade on the production bridge. We will need to change the DNS record for snowflake.torproject.net temporarily to the staging bridge, then later change it back. irl suggested setting a short TTL in advance of making the DNS changes.

I anticipate being finished with the upgrade and being able to restore the normal TTL by 2022-02-04.