message: [ocaml-gen] fix format string
diff: @@ -524,7 +524,7 @@ pub fn derive_ocaml_gen(item: TokenStream) -> TokenStream {
  // type ('field) scalar_challenge = { inner: 'field }
  // ```
  if generics_ocaml.len() == 1 {
  - format!("{ inner: {} }", generics_ocaml[0])
  + format!("{{ inner: {} }}", generics_ocaml[0])
  } else {
  generics_ocaml.join(" * ")
  }
  