When using "Arial", it is rendered bold

When using Arial in my source html, ie:

html { font-family: Arial }

I get a bold font when converted to PDF:


I tried adding an extra buildpack that includes Arial:


But it throws an alert that this will take effect in the next deploy.

**The question is:** how can I force a rebuild or redeployment if I used the Heroku Button for deploying url-to-pdf-api ?