add bug 1902375 to 5.2 release notes

Author: justdave

_releases/5.2.html

@@ -534,6 +534,8 @@ <h4>Enhancements for Administrators and Developers</h4>
   <li><strong>Installation:</strong> The <code>testserver.pl</code> script will
     now work with self-signed SSL certificates if you pass the
     <code>--self-signed</code> option on the command line. (<a href="https://bugzilla.mozilla.org?show_bug.cgi?id=1851398">Bug 1851398</a>)</li>
+  <li><strong>Installation:</strong> An foreign key error when upgrading from
+      versions prior to 3.0 to 5.0.6 or newer was fixed. (<a href="https://bugzilla.mozilla.org?show_bug.cgi?id=1902375">Bug 1902375</a></li>
 </ul>
 
 <h4 id="feat_webservices_other">WebService Changes</h4>