opam: bump version to 1.2, correct URLs
opam: bump version to 1.2, correct URLs

Signed-off-by: David Scott <63c9eb0ea83039690fefa11afe17873ba8278a56@unikernel.com>

djs55/ocaml-launchd,djs55/ocaml-launchd,mirage/ocaml-launchd,mirage/ocaml-launchd