Error When attempting to deploy to Heroku `django.core.exceptions.ImproperlyConfigured: Missing environment variable: SFDX_CLIENT_CALLBACK_URL`

[camerongoodman]

Error on initial push to Heroku after running git push heroku main
django.core.exceptions.ImproperlyConfigured: Missing environment variable: SFDX_CLIENT_CALLBACK_URL

Line 179 in the setup documentation heroku-setup.md says to use SF_CALLBACK_URL however looks like it needs SFDX_CLIENT_CALLBACK_URL instead.