This error usually comes when we have different versions of migrations file on heroku and local.
For example we have 0004_somename.py on local and say 0005_somename on heroku and this happens when we accidently run the command heroku run python manage.py migrations.
heroku run python manage.py migrations
First do makemigrations and migrate locally and then add those newly created migrations file using git and run only migrate command on heroku.
Just rollback the version of app before that mistake was done and then again do migrate.
You can see the version of your app at different time from heroku website.
For example rollback to v30 using below command
$ heroku rollback v30
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