Allow sebastian/comparator 6 (to allow PHPUnit 11)

[Jean85]

This is a blocker for end users to upgrade to PHPUnit 11.

This new major of sebastian/comparator does not have any meaningful change, as you can see:

• from the changelog: https://github.com/sebastianbergmann/comparator/blob/main/ChangeLog.md#600---2024-02-02
• or the full diff (only CS fixes): https://github.com/sebastianbergmann/comparator/compare/5.0.1...6.0.0

[EDIT] Same goes for sebastian/recursion-context:

• changelog: https://github.com/sebastianbergmann/recursion-context/blob/main/ChangeLog.md#600---2024-02-02
• full diff: https://github.com/sebastianbergmann/recursion-context/compare/5.0.0...6.0.0

[XWB]

Can we have a new release with these changes?