Update simplecov requirement from ~> 0.17.1 to ~> 0.18.0
Update simplecov requirement from ~> 0.17.1 to ~> 0.18.0

Updates the requirements on [simplecov](https://github.com/colszowka/simplecov) to permit the latest version.
- [Release notes](https://github.com/colszowka/simplecov/releases)
- [Changelog](https://github.com/colszowka/simplecov/blob/master/CHANGELOG.md)
- [Commits](https://github.com/colszowka/simplecov/compare/v0.17.1...v0.18.0)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
deanwilson/puppet-lint-no_symbolic_file_modes-check