I have a spring boot gradle app which I could run successfully on my PC by doing:
heroku local
It can also deploy on heroku successfully wh
According to the documentation:
The Gradle buildpack will automatically detect the use of the Spring Boot and Ratpack web frameworks.
The web command should be overridden only if needed. If you're using Spring Boot, you shouldn't need to specify a Procfile at all.
Delete it, and get your app running without further configuration.