Update snowflake version and prefs to do nat discovery at the client

This will update the snowflake version to include the changes merged from tpo/anti-censorship/pluggable-transports/snowflake#34129 (closed)

This also requires an update to the snowflake preferences to add new STUN servers that implement RFC 5780 (https://bugs.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/30579).