Update packages/pbkdf/pbkdf.2.0.0/opam

Author: mseri

packages/pbkdf/pbkdf.2.0.0/opam

@@ -15,7 +15,7 @@ depends: [
   "ocaml" {>= "4.07.0"}
   "dune" {>= "1.8.0"}
   "mirage-crypto" {>= "1.0.0"}
-  "digestif"
+  "digestif" {>= "1.2"}
   "alcotest" {with-test & >= "0.8.1"}
   "ohex" {with-test}
 ]