l10n: text for `--help` & `--version` options is not localized

[cakebaker]

When running, for example, LANG=fr_FR.UTF-8 cargo run -q rm --help, the help text for the --help and --version options is not localized:

// snipped
  -d, --dir                   supprimer les répertoires vides
  -v, --verbose               expliquer ce qui est fait
  -h, --help                  Print help
  -V, --version               Print version

The translations already exist in the .ftl files in uucore/locales, but are never used.