Update jangregor/phpstan-prophecy requirement from ^0.6 to ^0.8 (#73)
Update jangregor/phpstan-prophecy requirement from ^0.6 to ^0.8 (#73)

Updates the requirements on [jangregor/phpstan-prophecy](https://github.com/Jan0707/phpstan-prophecy) to permit the latest version.
- [Release notes](https://github.com/Jan0707/phpstan-prophecy/releases)
- [Changelog](https://github.com/Jan0707/phpstan-prophecy/blob/master/CHANGELOG.md)
- [Commits](https://github.com/Jan0707/phpstan-prophecy/compare/0.6.0...0.8.1)

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

Co-authored-by: dependabot[bot] <1c358da00a777d4e9898c1280ab801e2df165188@users.noreply.github.com>
ramsey/collection,ramsey/collection