Update opam

Author: codinuum

packages/vlt/vlt.0.2.3/opam

@@ -11,7 +11,6 @@ tags: ["logging"]
 homepage: "https://github.com/codinuum/vlt"
 doc: "https://github.com/codinuum/vlt/README.md"
 bug-reports: "https://github.com/codinuum/vlt/issues"
-available: os-family != "windows"
 depends: [
   "ocaml" {>= "4.14"}
   "dune" {>= "3.7"}