Update SEE ALSO sections for resolver.{3,5} and hosts.5

The mentioned document "Name Server Operations Guide for BIND" is
outdated, so remove it from the SEE ALSO section of hosts.5
and resolver.{3,5}.

PR: 266360
Reported by: Graham Perrin <grahamperrin at FreeBSD dot org>
Reviewed by: karels
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D36557