opam: downgrade omd to 1.3.1 (avoid 2.0.0~alpha)

Author: yasunariw

monorobot.opam

@@ -26,7 +26,7 @@ depends: [
  "stdio"
  "uri"
  "ocamlformat" {dev & = "0.13.0"}
- "omd" {< "2.0.0"}
+ "omd" {<= "1.3.1"}
  "yojson"
 ]
 build: ["dune" "build" "-p" name]