Update cucumber requirement from ~> 5.0 to ~> 6.0
Update cucumber requirement from ~> 5.0 to ~> 6.0

Updates the requirements on [cucumber](https://github.com/cucumber/cucumber-ruby) to permit the latest version.
- [Release notes](https://github.com/cucumber/cucumber-ruby/releases)
- [Changelog](https://github.com/cucumber/cucumber-ruby/blob/master/CHANGELOG.md)
- [Commits](https://github.com/cucumber/cucumber-ruby/compare/v5.0.0...v6.0.0)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
mvz/keep_up,mvz/keep_up