docs: update several URLs to point to docs.named-data.net

Change-Id: I4bab897f17e2b929675119198c9eab0309b6cc3e
diff --git a/nfd.conf.sample.in b/nfd.conf.sample.in
index e929dc9..660beb2 100644
--- a/nfd.conf.sample.in
+++ b/nfd.conf.sample.in
@@ -352,7 +352,7 @@
   ;   ; trust-anchors, which are briefly defined in this file.  For more information refer to
   ;   ; validator configuration file format documentation:
   ;   ;
-  ;   ;    https://named-data.net/doc/ndn-cxx/current/tutorials/security-validator-config.html
+  ;   ;    https://docs.named-data.net/ndn-cxx/current/tutorials/security-validator-config.html
   ;   ;
   ;   ; A trust-anchor is a pre-trusted certificate.  This can be any certificate that is the
   ;   ; root of certification chain (e.g., NDN testbed root certificate) or an existing