How do I update bors-ng in Heroku?

Hi

We set up Bors-ng using the "Deploy to Heroku" button in your Github readme. It has been working great for some time but now we would like to update our Bors-ng version to the latest version. How can we update the version that is running in our Heroku instance? I tried the instructions I found here https://f-a.nz/dev/update-deploy-to-heroku-app/ (basically download the Github repo, add a new Heroku remote and push master to this remote) but I got a "Push rejected" message (I guess that the master branch is somehow protected)

Thanks in advance for your help!!

Carlos

In case it helps someone, I was able to solve this by clearing the Heroku build cache https://help.heroku.com/18PI5RSY/how-do-i-clear-the-build-cache