N°6934 - Symfony 6.4 - upgrade Symfony bundles to 6.4 (#580)

* Update Symfony lib to version ~6.4.0
* Update code missing return type
* Add an iTop general configuration entry to store application secret (Symfony mandatory parameter)
* Use dependency injection in ExceptionListener & UserProvider classes

lib/symfony/css-selector/Node/ElementNode.php

@@ -23,8 +23,8 @@ namespace Symfony\Component\CssSelector\Node;
  */
 class ElementNode extends AbstractNode
 {
-    private $namespace;
-    private $element;
+    private ?string $namespace;
+    private ?string $element;
 
     public function __construct(string $namespace = null, string $element = null)
     {
@@ -42,9 +42,6 @@ class ElementNode extends AbstractNode
         return $this->element;
     }
 
-    /**
-     * {@inheritdoc}
-     */
     public function getSpecificity(): Specificity
     {
         return new Specificity(0, 0, $this->element ? 1 : 0);