[sledge] Build: Add version constraint on apron to fix macos build

Summary: v0.9.13 is the first to include https://github.com/antoinemine/apron/pull/28

Reviewed By: ngorogiannis

Differential Revision: D23669920

fbshipit-source-id: 3041bdd82

sledge/sledge.opam

@@ -10,7 +10,7 @@ build: [
 ]
 depends: [
   "ocaml"
-  "apron"
+  "apron" {>= "v0.9.13"}
   "base"
   "containers"
   "core" {>= "v0.14"}