old version otree should use redis when runprodserver

[zangguojun]

env: python 3.7.13 otree 2.1.28
I was the earliest user of Otree. When I deployed an old project on Heroku,

Procfile File

web: otree runprodserver1of2
worker: otree runprodserver2of2

heroku logs

I remember I did not install redis before
then how can I add redis in heroku? or not install redis?