Update longclaw's hard-coded IPv6 address
In 0.2.8.1-alpha, we added longclaw's IPv6 address as
ipv6=[2620:13:4000:8000:60:f3ff:fea1:7cff]:443
https://gitweb.torproject.org/tor.git/tree/src/or/config.c#n931
Now its descriptor says:
[2620:13:4000:8000:a800:ff:fef5:2213]:443
https://atlas.torproject.org/#details/74A910646BCEEFBCD2E874FC1DC997430F968145
Should we update this before the 0.2.8 release?