[Bugfix] Fixed a bug when attaching a feedback xml would not work wit…

…h symfony mailer

src/Resources/contao/forms/ExposeForm.php

@@ -452,7 +452,7 @@ protected function attachFeedbackXml($objRealEstate, $arrSubmitted)
         (
             'tmp_name' => TL_ROOT . '/' . $filePath,
             'name'     => 'feedback.xml',
-            'type'     => 'xml'
+            'type'     => 'application/xml'
         );
     }