Update sebastian/comparator requirement
Update sebastian/comparator requirement

Updates the requirements on [sebastian/comparator](https://github.com/sebastianbergmann/comparator) to permit the latest version.
- [Release notes](https://github.com/sebastianbergmann/comparator/releases)
- [Changelog](https://github.com/sebastianbergmann/comparator/blob/master/ChangeLog.md)
- [Commits](https://github.com/sebastianbergmann/comparator/commits/2.1.3)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
WyriHaximus/reactphp-child-process-promise