message: refactor(html/parser): Resolve TODO
diff: @@ -7681,11 +7681,10 @@ where
  }
  fn append_node(&self, parent: &RcNode, child: RcNode) {
  - let _previous_parent = child.parent.replace(Some(Rc::downgrade(parent)));
  + let previous_parent = child.parent.replace(Some(Rc::downgrade(parent)));
  - // TODO fix me
  // Invariant: child cannot have existing parent
  - // assert!(previous_parent.is_none());
  + assert!(previous_parent.is_none());
  parent.children.borrow_mut().push(child);
  }
  