DoHEndpointFromIP mapped the entire 2606:1a40::/48 range to a
dns.controld.com/<id> DoH URL, but the ID-encoded addresses in that range
are legacy plaintext-DNS endpoints that refuse :443. They now fall through
as ordinary port-53 resolvers; the free anycast freedns.controld.com/pN
addresses still upgrade via exact match.
Fixes#20433
Signed-off-by: Brendan Creane <bcreane@gmail.com>