its ok, I have found it:
moodle/login/index_form.html
remove lines 97 -106
<?php if (!empty($potentialidps)) { ?>
<div class="subcontent potentialidps">
<h6><?php print_string('potentialidps', 'auth'); ?></h6>
<div class="potentialidplist">
<?php foreach ($potentialidps as $idp) {
echo '<div class="potentialidp"><a href="' . $idp['url']->out() . '" title="' . $idp['name'] . '">' . $OUTPUT->render($idp['icon'], $idp['name']) . ' ' . $idp['name'] . '</a></div>';
} ?>
</div>
</div>
<?php } ?>