Update the list of RFC 5780 compatible STUN servers

When looking at some client logs, I noticed several of the following messages:

 WARNING: 2023/11/02 18:40:42 Error: NAT discovery feature not supported by this server

It appears that several of our default STUN servers at the client no longer support this feature. This may partially explain the high number of unknown client NAT types that we see in the metrics.