message: remove useless MutationObserver config
diff: @@ -223,17 +223,10 @@ export function initMixin(BScroll) {
  BScroll.prototype._initDOMObserver = function () {
  if (typeof MutationObserver !== 'undefined') {
  let observer = new MutationObserver((mutations) => {
  - let shouldRefresh = mutations.some((mutation) => {
  - return mutation.type !== 'attributes'
  - })
  - if (shouldRefresh) {
  this.refresh()
  - }
  })
  const config = {
  - attributes: true,
  childList: true,
  - characterData: true,
  subtree: true
  }
  observer.observe(this.scroller, config)
  