Simply add a ‘tested’ value to the $packages array, like so:
$packages['your-plugin'] = array(
'versions' => array(
'x.x' => array(
...
'tested' => '3.1.1', // highest version of WP your plugin works with
And then, reflect that change in the ‘plugin_information’ check further down in the document:
if ($action == 'plugin_information') {
$data = new stdClass;
...
$data->tested = $latest_package['tested']; // pull in the value from $packages
That’s it. Worked for me anyway.
Good luck!