Remove beta.tailscale.net

[danderson]

(for once, wearing my day job hat not my contributing code hat)

Following up on commitment in #1453. I originally submitted beta.tailscale.net for inclusion, with a note that despite the name, it was being used for production hosting and that we were working on migrating off it and onto the other suffixes Tailscale has listed. That migration is now done, so beta.tailscale.net can be removed.

[wdhdev]

Are you able to update the _psl TXT record?

[simon-friedberger]

This would be a good opportunity to update the email address to something that stays reachable in case you leave tailscale.

[danderson]

Oops, didn't realize we do _psl updates for removal as well. Done, although recursive resolvers may still have the old value cached for ~1h:

> dig +noall +answer tailscale.net NS
tailscale.net.		172800	IN	NS	ns-91.awsdns-11.com.
tailscale.net.		172800	IN	NS	ns-932.awsdns-52.net.
tailscale.net.		172800	IN	NS	ns-1660.awsdns-15.co.uk.
tailscale.net.		172800	IN	NS	ns-1192.awsdns-21.org.

> dig +noall +answer _psl.beta.tailscale.net TXT @ns-932.awsdns-52.net
_psl.beta.tailscale.net. 3600	IN	TXT	"https://github.com/publicsuffix/list/pull/2216"

I also updated the contact email to reach the infrastructure team in general, not just me. Thanks for pointing that out!