Fix NodeIterator pre-remove steps for ancestors of root

Generalize the first early-return clause so it bails when toBeRemovedNode
is an inclusive ancestor of the iterator's root, not only when it equals
the root. Implementations and the WPT test (NodeIterator-removal.html)
already do this.

Additional tests: web-platform-tests/wpt#60997.

Closes #907.

Author: annevk

dom.bs

@@ -10320,8 +10320,9 @@ given a {{NodeIterator}} object <var>nodeIterator</var> and <a for=/>node</a>
 
 <ol>
  <li><p>If <var>toBeRemovedNode</var> is not an <a for=tree>inclusive ancestor</a> of
- <var>nodeIterator</var>'s <a for=NodeIterator>reference</a>, or <var>toBeRemovedNode</var> is
- <var>nodeIterator</var>'s <a for=traversal>root</a>, then return.
+ <var>nodeIterator</var>'s <a for=NodeIterator>reference</a>, or <var>toBeRemovedNode</var> is an
+ <a for=tree>inclusive ancestor</a> of <var>nodeIterator</var>'s <a for=traversal>root</a>, then
+ return.
 
  <li>
   <p>If <var>nodeIterator</var>'s <a for=NodeIterator>pointer before reference</a> is true: