Remove dead code from contact.install

  $config = \Drupal::config('contact.form.feedback');
  // Update the recipients if the default configuration entity has been created.
  // We should never rely on default config entities as during enabling a module
  // during config sync they will not exist.
  if (!$config->isNew()) {
    \Drupal::config('contact.form.feedback')->set('recipients', array($site_mail))->save();
  }

Is dead code