fix: close stderr in [run_in_directory]

Otherwise we're going to leak a file descriptor

Signed-off-by: Rudi Grinberg <[email protected]>

<!-- ps-id: 2bb24191-5229-4cc4-b689-43453c181f6b -->

ocaml-lsp-server/src/ocaml_lsp_server.ml

@@ -929,6 +929,7 @@ let run_in_directory ~prog ~prog_is_quoted:_ ~args ~cwd ?stdin ?stdout ?stderr (
   in
   Unix.close stdin;
   if should_close_stdout then Unix.close stdout;
+  Option.iter stderr ~f:Unix.close;
   `Finished res
 ;;