框架本地无法运行，修复尝试

vendor/phpoffice/math/src/Math/Reader/MathML.php

@@ -10,7 +10,6 @@ use PhpOffice\Math\Element;
 use PhpOffice\Math\Exception\InvalidInputException;
 use PhpOffice\Math\Exception\NotImplementedException;
 use PhpOffice\Math\Math;
-use PhpOffice\Math\Reader\Security\XmlScanner;
 
 class MathML implements ReaderInterface
 {
@@ -23,17 +22,8 @@ class MathML implements ReaderInterface
     /** @var DOMXPath */
     private $xpath;
 
-    /** @var XmlScanner */
-    private $xmlScanner;
-
-    public function __construct()
-    {
-        $this->xmlScanner = XmlScanner::getInstance();
-    }
-
     public function read(string $content): ?Math
     {
-        $content = $this->xmlScanner->scan($content);
         $content = str_replace(
             [
                 '⁢',
@@ -45,7 +35,7 @@ class MathML implements ReaderInterface
         );
 
         $this->dom = new DOMDocument();
-        $this->dom->loadXML($content);
+        $this->dom->loadXML($content, LIBXML_DTDLOAD);
 
         $this->math = new Math();
         $this->parseNode(null, $this->math);