Update security.txt expires field

Signed-off-by: Joas Schilling <coding@schilljs.com>

apps/settings/lib/WellKnown/SecurityTxtHandler.php

@@ -38,10 +38,11 @@ class SecurityTxtHandler implements IHandler {
 		}
 
 		$response = "Contact: https://hackerone.com/nextcloud
-Expires: 2021-12-31T23:00:00.000Z
+Expires: 2023-04-31T23:00:00.000Z
 Acknowledgments: https://hackerone.com/nextcloud/thanks
 Acknowledgments: https://github.com/nextcloud/security-advisories/security/advisories
-Policy: https://hackerone.com/nextcloud";
+Policy: https://hackerone.com/nextcloud
+Preferred-Languages: en";
 
 		return new GenericResponse(new TextPlainResponse($response, 200));
 	}