Fix https://github.com/phpmyadmin/phpmyadmin-security/issues/260 Stored Cross-Site Scripting (XSS) in navigation tree

Signed-off-by: Madhura Jayaratne <madhura.cj@gmail.com>

libraries/classes/Navigation/NavigationTree.php

@@ -762,7 +762,7 @@ class NavigationTree
                 }
 
                 $groups[$key] = new Node(
-                    $key,
+                    htmlspecialchars($key),
                     Node::CONTAINER,
                     true
                 );