Revert "set some properties in AST Node ctor - workaround microsoft/T…

…ypeScript#26811"

This reverts commit 5a7292e.

src/language-html/ast.js

@@ -7,21 +7,6 @@ const NODES_KEYS = {
 
 class Node {
   constructor(props = {}) {
-    /**
-     * define some class properties here, to work around
-     * https://github.com/microsoft/TypeScript/issues/26811
-     */
-    this.index = undefined;
-    this.siblings = undefined;
-    this.prev = undefined;
-    this.next = undefined;
-    this.parent = undefined;
-
-    this.name = undefined;
-    this.namespace = undefined;
-    this.hasExplicitNamespace = undefined;
-    this.children = undefined;
-
     for (const key of Object.keys(props)) {
       const value = props[key];
       if (key in NODES_KEYS) {