update constraint in opam file
update constraint in opam file

the-lambda-church/merlin,ocaml/merlin,ocaml/merlin,ocaml/merlin,dra27/merlin,the-lambda-church/merlin,dra27/merlin,dra27/merlin,dra27/merlin,rgrinberg/merlin,rgrinberg/merlin,ocaml/merlin,rgrinberg/merlin,the-lambda-church/merlin,rgrinberg/merlin