Update network6-add.json

doc/api/network6-add.json

@@ -2,7 +2,7 @@
      "name": "network6-add",
     "brief": "The network6-add command is used to add a new shared network.",
     "description": "See <xref linkend=\"idp75\"/>",
-    "support": [ "kea-dhcp4", "kea-dhcp6" ],
+    "support": [ "kea-dhcp6" ],
     "avail": "1.3.0",
     "hook": "subnet_cmds",
     "cmd-syntax": "{