Update lease4-get-all.json

doc/api/lease4-get-all.json

 {
     "name": "lease4-get-all",
     "brief": "lease4-get-all is used to retrieve all IPv4 leases or all leases for the specified set of subnets.",
-    "description": "See <xref linkend=\"lease4-get-all\"/>",
+    "description": "See <xref linkend=\"idp59\"/>",
     "support": [ "kea-dhcp4", "kea-dhcp6" ],
     "avail": "1.4.0",
     "hook": "lease_cmds",