php artisan db:seed
The cause of this is because Heroku only installs the dependencies that's in "require" so what you have to do is move "fzaninotto/faker" to "require-dev" and update the composer file for the latest composer.lock before pushing the latest changes to Heroku.
Full Steps by Steps Guide
- Move "fzaninotto/faker" from "require-dev" to "require"
- Update composer with "composer update" (this will update composer.lock file)
- Push the changes to GitHub / Heroku then deploy it to production
- Run the database seed command