message: fix: do not collapse top level on Collapse All in json samples
  * fix: update collapseAll method
  to avoid collapsing whole object/array
  * fix: remove extra "slice()" call
diff: @@ -57,11 +57,10 @@ class Json extends React.PureComponent<JsonProps> {
  collapseAll = () => {
  const elements = this.node.getElementsByClassName('collapsible');
  - for (const expanded of Array.prototype.slice.call(elements)) {
  - // const collapsed = elements[i];
  - if ((expanded.parentNode as Element)!.classList.contains('redoc-json')) {
  - continue;
  - }
  + // skip first item to avoid collapsing whole object/array
  + const elementsArr = Array.prototype.slice.call(elements, 1);
  +
  + for (const expanded of elementsArr) {
  (expanded.parentNode as Element)!.classList.add('collapsed');
  }
  };
  