Bump isort from 4.3.17 to 4.3.18 in /{{cookiecutter.app_name}}

Bumps [isort](https://github.com/timothycrosley/isort) from 4.3.17 to 4.3.18.
- [Release notes](https://github.com/timothycrosley/isort/releases)
- [Changelog](https://github.com/timothycrosley/isort/blob/develop/CHANGELOG.md)
- [Commits](https://github.com/timothycrosley/isort/compare/4.3.17...4.3.18

)

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