Fix types for changes in @types/unist

Author: wooorm

lib/util.js

@@ -12,6 +12,7 @@ import {convertElement} from 'hast-util-is-element'
  * @returns {node is Parent}
  */
 export function parent(node) {
+  // @ts-expect-error: hush.
   return Array.isArray(node.children)
 }