Elgg\Database\UsersTable::removeAdmin PHP Method

    public function removeAdmin($user_guid)
    {
        $user = get_entity($user_guid);
        if (!$user instanceof ElggUser || !$user->canEdit()) {
            return false;
        }
        if (!$this->events->trigger('remove_admin', 'user', $user)) {
            return false;
        }
        $query = "\n\t\t\tUPDATE {$this->table}\n\t\t\tSET admin = 'no'\n\t\t\tWHERE guid = :guid\n\t\t";
        $params = [':guid' => (int) $user_guid];
        _elgg_invalidate_cache_for_entity($user_guid);
        _elgg_invalidate_memcache_for_entity($user_guid);
        if ($this->db->updateData($query, true, $params)) {
            return true;
        }
        return false;
    }