Issue #3467661: Corrects language code passed from DrupalMailHandler.

Closes #3467661

src/Logger/Handler/DrupalMailHandler.php

@@ -55,7 +55,7 @@ class DrupalMailHandler extends MailHandler {
       'content' => $content,
       'records' => $records,
     ];
-    $mail->mail('monolog', 'default', $this->to, $default_language->getName(),
+    $mail->mail('monolog', 'default', $this->to, $default_language->getId(),
       $params);
   }