Bug: line over 90 characters with extension point

[ceastlund]

Describe the bug The nested expression should be wrapped, the line exceeds 90 characters.

let _ =
  [%str
    let () = very_long_function_name__________________ very_long_argument_name____________]
;;

How to Reproduce ocamlformat built from 99444f3054e29e2322e56b23422e9984a378170f using --profile=janestreet.