CNR: Update docs with proper Nameserver example (#3592)

Author: mejofi

documentation/provider/cnr.md

@@ -90,10 +90,9 @@ DEFAULTS(
 );
 
 D("example.com", REG_CNR, DnsProvider(DSP_CNR),
-    NAMESERVER("ns1.rrpproxy.net"),
-    NAMESERVER("ns2.rrpproxy.net"),
-    NAMESERVER("ns3.rrpproxy.net"),
-    NAMESERVER("ns4.rrpproxy.net"),
+    NAMESERVER("ns1.rrpproxy.net."),
+    NAMESERVER("ns2.rrpproxy.net."),
+    NAMESERVER("ns3.rrpproxy.net."),
     A("elk1", "10.190.234.178"),
     A("test", "56.123.54.12"),
 );