Remove langcode manipulation by Path widget

Follow-up from #2201051: Convert path.module form alters to a field widget.

      // Entity language needs special care. Since the language of the URL alias
      // depends on the entity language, and the entity language can be switched
      // right within the same form, we need to conditionally overload the
      // originally assigned URL alias language.
      // @see \Drupal\content_translation\ContentTranslationController::entityFormAlter()
      if (isset($form_state['values']['langcode'])) {
        $form_builder->setValue($element['langcode'], $form_state['values']['langcode'], $form_state);
      }