clearTrackHtml (player) {
    if (player) {
      if (player.captionsButton) {
        player.captionsButton.remove();
      }
      if (player.chaptersButton) {
        player.chaptersButton.remove();
      }
    }
  }
Feature destructor.

Always has to be prefixed with `clean` and the name that was used in MepDefaults.features list
@param {MediaElementPlayer} player