Update opam

Author: toots

packages/duppy/duppy.0.9.3/opam

@@ -7,6 +7,7 @@ license: "LGPL-2.1-only"
 homepage: "https://github.com/savonet/ocaml-duppy"
 bug-reports: "https://github.com/savonet/ocaml-duppy/issues"
 depends: [
+  "ocaml" {>= "4.07.0"}
   "dune" {>= "2.7"}
   "pcre"
   "odoc" {with-doc}