libxml_disable_entity_loader() is deprecated

Problem/Motivation

Updating to php 8 raises a warning

Message Deprecated function: Function libxml_disable_entity_loader() is deprecated in Drupal\views_xml_backend\Plugin\views\query\Xml->createDomDocument() (line 573 of /app/docroot/modules/contrib/views_xml_backend/src/Plugin/views/query/Xml.php)

Steps to reproduce

Update the server to use php 8 and later

Proposed resolution

On code that only runs on PHP 8.0 and later, it is now safe to remove all function calls.
Call libxml_disable_entity_loader conditionally on php versions lower than 8