Fix return value in stub file for DOMNodeList::item

Not explicitly documenting the possibility of returning DOMElement causes
the Intelephense linter (a popular PHP linter with ~9 million downloads:
https://marketplace.visualstudio.com/items?itemName=bmewburn.vscode-intelephense-client)
to think this code is bad:

  $xp->query("whatever")->item(0)->getAttribute("foo");

DOMNode does not have getAttribute (while DOMElement does).
Documenting the DOMElement return type should fix Intelephense's linter.

Closes GH-11342.

Author: divinity76

NEWS

@@ -10,6 +10,7 @@ PHP                                                                        NEWS
     and segfaults with replaceWith). (nielsdos)
   . Fixed bug GH-10234 (Setting DOMAttr::textContent results in an empty
     attribute value). (nielsdos)
+  . Fix return value in stub file for DOMNodeList::item. (divinity76)
 
 - Opcache:
   . Fix allocation loop in zend_shared_alloc_startup(). (nielsdos)

ext/dom/php_dom.stub.php

@@ -232,7 +232,7 @@ public function count(): int {}
 
     public function getIterator(): Iterator {}
 
-    /** @return DOMNode|DOMNameSpaceNode|null */
+    /** @return DOMElement|DOMNode|DOMNameSpaceNode|null */
     public function item(int $index) {}
 }
 

ext/dom/php_dom_arginfo.h

@@ -1,5 +1,5 @@
 /* This is a generated file, edit the .stub.php file instead.
- * Stub hash: 74698bea9c5e0635cf91345e8512b9677489510c */
+ * Stub hash: a62e383b05df81ea245a7993215fb8ff4e1c7f9d */
 
 ZEND_BEGIN_ARG_WITH_RETURN_OBJ_INFO_EX(arginfo_dom_import_simplexml, 0, 1, DOMElement, 0)
 	ZEND_ARG_TYPE_INFO(0, node, IS_OBJECT, 0)