Avoid pulling sebastian/comparator v5 not compatible with phpunit v10

[DesignPond]

Q	A
Bug fix?	no
New feature?	no
BC breaks?	no
Deprecations?	no
Related tickets
Documentation
License	MIT

What's in this PR?

Avoid pulling sebastian/comparator version 5 which is not compatible with phpunit version 10

Why?

Running the project locally fails to pass the tests as it's pulling phpunit version 10 which is not compatible with sebastian/comparator version 5 for the SebastianBergmann\Comparator\Comparator::assertEquals assertion.

How to reproduce it

composer inst
composer test

PHP Fatal error:  Declaration of SebastianBergmann\Comparator\ArrayComparator::assertEquals(mixed $expected, mixed $actual, float $delta = 0, bool $canonicalize = false, bool $ignoreCase = false, array &$processed = []): void must be compatible with SebastianBergmann\Comparator\Comparator::assertEquals($expected, $actual, $delta = 0, $canonicalize = false, $ignoreCase = false) in /Users/cindyleschaud/Projects/discovery/vendor/sebastian/comparator/src/ArrayComparator.php on line 36

Checklist

• Updated CHANGELOG.md to describe BC breaks / deprecations | new feature | bugfix
• Documentation pull request created (if not simply a bugfix)

To Do

• If the PR is not complete but you want to discuss the approach, list what remains to be done here

[Nyholm]

Lovely. This is a good temporary solution until PHPUnit Bridge supports PHPUnit 10 properly.

[Nyholm]

Failing test is not related. See #256