fix(notifications): set mark-all-as-read parameter to be podcast_id instead of actor_id

<?= $this->endSection() ?>

<?= $this->section('headerRight') ?>

<Button uri="<?= route_to('notification-mark-all-as-read', $podcast->actor_id) ?>" variant="primary"><?= lang('Notifications.mark_all_as_read') ?></Button>

<Button uri="<?= route_to('notification-mark-all-as-read', $podcast->id) ?>" variant="primary"><?= lang('Notifications.mark_all_as_read') ?></Button>

<?= $this->endSection() ?>

<?= $this->section('content') ?>