Update lease6-del.json

doc/api/lease6-del.json

@@ -11,5 +11,5 @@
         \"ip-address\": \"192.0.2.202\"
     }
 }",
-    "cmd-comment": "leaseX-del returns a result that indicates a outcome of the operation. It has one of the following values: 0 (success), 1 (error) or 3 (empty).",
+    "cmd-comment": "lease6-del returns a result that indicates a outcome of the operation. It has one of the following values: 0 (success), 1 (error) or 3 (empty).",
 }
\ No newline at end of file