Update quickcheck requirement from 0.7 to 0.8

Updates the requirements on [quickcheck](https://github.com/BurntSushi/quickcheck) to permit the latest version.
- [Release notes](https://github.com/BurntSushi/quickcheck/releases)
- [Commits](https://github.com/BurntSushi/quickcheck/commits/quickcheck_macros-0.8.0)

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