Docs: Update NAMESERVER() to not mention IPs.

docs/_functions/domain/NAMESERVER.md

@@ -2,22 +2,25 @@
 name: NAMESERVER
 parameters:
   - name
-  - ip
   - modifiers...
 ---
 
-NAMESERVER NS instructs DNSControl to inform the domain's registrar where to find this zone.
+`NAMESERVER()` instructs DNSControl to inform the domain's registrar where to find this zone.
 For some registrars this will also add NS records to the zone itself.
 
-`ip` is optional, and is only required if glue records need to be generated in the parent zone.
+This takes exactly one argument: the name of the nameserver. It must end with
+a "." if it is a FQDN, just like all targets.
+
+This is different than the `NS()` function, which inserts NS records
+in the current zone and accepts a label. It is useful for downward
+delegations. This is for informing upstream delegations.
 
 {% include startExample.html %}
 {% highlight js %}
 
 D("example.com", REGISTRAR, .... ,
-  NAMESERVER("ns1.myserver.com"),
+  NAMESERVER("ns1.myserver.com."),
-  NAMESERVER("ns2.example.com", "100.100.100.100"), // the server plus glue
+  NAMESERVER("ns2.myserver.com."),
-  A("www", "10.10.10.10"),
 );
 
 {%endhighlight%}