relax upper bounds on ppx_cstruct to match opam-repo

Author: avsm

ppx_cstruct.opam

@@ -17,13 +17,13 @@ build: [
 ]
 depends: [
   "ocaml" {>= "4.03.0"}
-  "dune" {build & >= "1.0"}
+  "dune"
   "cstruct" {=version}
   "ounit" {with-test}
   "ppx_tools_versioned" {>= "5.0.1"}
   "ocaml-migrate-parsetree"
-  "ppx_sexp_conv" {with-test & < "v0.13"}
-  "sexplib" {< "v0.13"}
+  "ppx_sexp_conv" {with-test}
+  "sexplib" {>="v0.9.0"}
   "cstruct-sexp" {with-test}
   "cstruct-unix" {with-test & =version}
   "stdlib-shims"