Bump supervisor from 4.0.3 to 4.0.4 in /{{cookiecutter.app_name}} (#521)

Bumps [supervisor](https://github.com/Supervisor/supervisor) from 4.0.3 to 4.0.4.
- [Release notes](https://github.com/Supervisor/supervisor/releases)
- [Changelog](https://github.com/Supervisor/supervisor/blob/master/CHANGES.rst)
- [Commits](https://github.com/Supervisor/supervisor/compare/4.0.3...4.0.4

)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>