lambdapi.2.2.1: fix bindlib lower bound

Author: fblanqui

packages/lambdapi/lambdapi.2.2.1/opam

@@ -52,7 +52,7 @@ depends: [
   "sedlex" {>= "2.2"}
   "alcotest" {with-test}
   "dedukti" {with-test & >= "2.7"}
-  "bindlib" {>= "5.0.1"}
+  "bindlib" {>= "6.0.0"}
   "timed" {>= "1.0"}
   "pratter" {>= "2.0.0" & < "3"}
   "camlp-streams" {>= "5.0"}