Fix minor section formatting mishap in SSH key email

Summary: Ref T10917. This is getting added as a link right now, which causes it to get `<a href>`'d in HTML mail. Add it as text instead.

Test Plan: Edited a key, examined HTML mail body carefully.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10917

Differential Revision: https://secure.phabricator.com/D15952

Author: epriestley

src/applications/auth/editor/PhabricatorAuthSSHKeyEditor.php

@@ -227,7 +227,7 @@ protected function buildMailBody(
 
     $body = parent::buildMailBody($object, $xactions);
 
-    $body->addLinkSection(
+    $body->addTextSection(
       pht('SECURITY WARNING'),
       pht(
         'If you do not recognize this change, it may indicate your account '.