Fix the OPAM file

See ocaml/opam-repository#24571

lbfgs.opam

@@ -1,15 +1,15 @@
 opam-version: "2.0"
 maintainer: "Christophe Troestler <Christophe.Troestler@umons.ac.be>"
 authors: [ "Christophe Troestler <Christophe.Troestler@umons.ac.be>" ]
-license: "LGPL-3.0 with OCaml linking exception"
+license: "LGPL-3.0-only WITH OCaml-LGPL-linking-exception"
 homepage: "https://github.com/Chris00/L-BFGS-ocaml"
 dev-repo: "git+https://github.com/Chris00/L-BFGS-ocaml.git"
 bug-reports: "https://github.com/Chris00/L-BFGS-ocaml/issues"
 doc: "https://Chris00.github.io/L-BFGS-ocaml/doc"
 tags: [ "science" "numerics" "optimization" "minimization" "maximization"
         "bound-constrained" "large-scale" ]
 build: [
-  ["dune" "subst"] {pinned}
+  ["dune" "subst"] {dev}
   ["dune" "build" "-p" name "-j" jobs]
   ["dune" "build" "@doc" "-p" name "-j" jobs] {with-doc}
 ]