Update stat-lease6-get.json

doc/api/stat-lease6-get.json

@@ -3,7 +3,7 @@
     "brief": "The stat-lease6-get command fetches lease statistics for a range
               of known IPv6 subnets.",
     "description": "See <xref linkend=\"command-stat-lease6-get\"/>",
-    "support": [ "kea-dhcp4", "kea-dhcp6" ],
+    "support": [ "kea-dhcp6" ],
     "avail": "1.4.0",
     "hook": "stat_cmds",
     "cmd-syntax": "{