Update lease4-add.json

doc/api/lease4-add.json

@@ -2,7 +2,7 @@
     "name": "lease4-add",
     "brief": "The lease4-add command adds a new IPv4 lease administratively.",
     "description": "See <xref linkend=\"command-lease4-add\"/>",
-    "support": [ "kea-dhcp4", "kea-dhcp6" ],
+    "support": [ "kea-dhcp4"],
     "avail": "1.3.0",
     "hook": "lease_cmds",
     "cmd-syntax": "{