Return on out-of-bounds dataTransfer.items.remove()

Tests: web-platform-tests/wpt#33737.

Closes #2925.

source

@@ -79651,6 +79651,9 @@ DND-v5:  <span>DataTransferItem</span>? <span data-x="dom-DataTransferItemList-a
    data-x="concept-dnd-rw">read/write mode</i>, throw an
    <span>"<code>InvalidStateError</code>"</span> <code>DOMException</code>.</p></li>
 
+   <li><p>If the <span>drag data store</span> does not contain an <var>index</var>th item, then
+   return.</p></li>
+
    <li><p>Remove the <var>index</var>th item from the <span>drag data store</span>.</p></li>
   </ol>