Merge pull request ocaml#22744 from samoht/bitcoin

bitcoin doesn't work on OCaml 5

Author: kit-ty-kate

packages/bitcoin/bitcoin.2.0/opam

@@ -19,7 +19,7 @@ build: [
 install: [[make "install"]]
 remove: [["ocamlfind" "remove" "bitcoin"]]
 depends: [
-  "ocaml"
+  "ocaml" {< "5.0"}
   "yojson" {< "2.0.0"}
   "cryptokit"
   "ocamlbuild" {build}