Have HTMLCollection::item() return an Element as per specification

Source/core/html/HTMLTableSectionElement.cpp

Index: Source/core/html/HTMLTableSectionElement.cpp
diff --git a/Source/core/html/HTMLTableSectionElement.cpp b/Source/core/html/HTMLTableSectionElement.cpp
index ce8d5dc090938734aafe41259c790ae4ee59981a..074ab6ecc56428f756fb1940090cb951cee4d493 100644
--- a/Source/core/html/HTMLTableSectionElement.cpp
+++ b/Source/core/html/HTMLTableSectionElement.cpp
@@ -86,7 +86,7 @@ void HTMLTableSectionElement::deleteRow(int index, ExceptionState& exceptionStat
     if (index == -1)
         index = numRows - 1;
     if (index >= 0 && index < numRows) {
-        RefPtr<Node> row = children->item(index);
+        RefPtr<Element> row = children->item(index);
         HTMLElement::removeChild(row.get(), exceptionState);
     } else {
         exceptionState.throwDOMException(IndexSizeError, "The provided index (" + String::number(index) + " is outside the range [-1, " + String::number(numRows) + "].");