Bump environs from 5.2.0 to 5.2.1 in /{{cookiecutter.app_name}} (#534)

Bumps [environs](https://github.com/sloria/environs) from 5.2.0 to 5.2.1.
- [Release notes](https://github.com/sloria/environs/releases)
- [Changelog](https://github.com/sloria/environs/blob/master/CHANGELOG.md)
- [Commits](https://github.com/sloria/environs/compare/5.2.0...5.2.1

)

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