Remove longclaw's IPv6 address, as it will soon change

Authority IPv6 addresses were originally added in 0.2.8.1-alpha.

This leaves 3/8 directory authorities with IPv6 addresses, but there
are also 52 fallback directory mirrors with IPv6 addresses.

Resolves 19760.

changes/longclaw-ipv6

@@ -0,0 +1,6 @@
+  o Minor features (directory authorities):
+    - Remove longclaw's IPv6 address, as it will soon change.
+      Authority IPv6 addresses were originally added in 0.2.8.1-alpha.
+      This leaves 3/8 directory authorities with IPv6 addresses, but there
+      are also 52 fallback directory mirrors with IPv6 addresses.
+      Resolves 19760.

src/or/config.c

@@ -928,7 +928,6 @@ static const char *default_authorities[] = {
     "154.35.175.225:80 CF6D 0AAF B385 BE71 B8E1 11FC 5CFF 4B47 9237 33BC",
   "longclaw orport=443 "
     "v3ident=23D15D965BC35114467363C165C4F724B64B4F66 "
-    "ipv6=[2620:13:4000:8000:60:f3ff:fea1:7cff]:443 "
     "199.254.238.52:80 74A9 1064 6BCE EFBC D2E8 74FC 1DC9 9743 0F96 8145",
   NULL
 };