Remove mpyw/phpunit-patch-serializable-comparison dev dependency

Problem/Motivation

#3272768: Convert to JSON data storage (D9) → converted data storage from serialized to JSON, so the mpyw/phpunit-patch-serializable-comparison dev dependency is no longer necessary

Proposed resolution

Remove mpyw/phpunit-patch-serializable-comparison dev dependency

Remaining tasks

1. Create a merge request
2. Review
3. Commit

User interface changes

None

API changes

None

Data model changes

None