app/Template/group/dissociate.php

<div class="page-header">
    <h2><?= t('Remove user from group "%s"', $group['name']) ?></h2>
</div>
<div class="confirm">
    <p class="alert alert-info"><?= t('Do you really want to remove the user "%s" from the group "%s"?', $user['name'] ?: $user['username'], $group['name']) ?></p>

    <?= $this->modal->confirmButtons(
        'GroupListController',
        'removeUser',
        array('group_id' => $group['id'], 'user_id' => $user['id'])
    ) ?>
</div>