I think this is the text from Chapter 8 of Session 13:
Now as to the reception of the sacrament, it was always the custom in the Church of God, that laymen should receive the communion from priests; but that priests when celebrating should communicate themselves; which custom, as coming down from an apostolical tradition, ought with justice and reason to be retained.
Yes, that’s the only passage referencing “apostolic tradition” in connection with the Eucharist AFAIK.