Update function signature to match interface

When running `php bin/magento setup:di:compile` the following error is thrown:

Compilation was started.
Repositories code generation... 1/8 [===>------------------------]  12% 1 sec 100.0 MiBPHP Fatal error:  Declaration of Magento\PageBuilder\Model\Dom\NodeList::item($index): ?Magento\PageBuilder\Model\Dom\Adapter\ElementInterface must be compatible with Magento\PageBuilder\Model\Dom\Adapter\NodeListInterface::item(int $index): ?Magento\PageBuilder\Model\Dom\Adapter\ElementInterface in /var/www/html/vendor/magento/module-page-builder/Model/Dom/NodeList.php on line 19

Fatal error: Declaration of Magento\PageBuilder\Model\Dom\NodeList::item($index): ?Magento\PageBuilder\Model\Dom\Adapter\ElementInterface must be compatible with Magento\PageBuilder\Model\Dom\Adapter\NodeListInterface::item(int $index): ?Magento\PageBuilder\Model\Dom\Adapter\ElementInterface in /var/www/html/vendor/magento/module-page-builder/Model/Dom/NodeList.php on line 19

Author: fredden

app/code/Magento/PageBuilder/Model/Dom/NodeList.php

@@ -44,7 +44,7 @@ public function __construct(
     /**
      * @inheritDoc
      */
-    public function item($index): ?ElementInterface
+    public function item(int $index): ?ElementInterface
     {
         return $this->objectManager->create(ElementInterface::class, [ 'element' => $this->nodeList->item($index) ]);
     }