feat: Add support for PHP 8.3

[dplewis]

New Pull Request Checklist

• [ ] I am not disclosing a vulnerability.
• [ ] I am creating this PR in reference to an issue.

Issue Description

PHP 8.3 was released in November 2023.

Approach

• Add PHP 8.3 to CI
• Fix relative time flaky test

[parse-github-assistant[bot]]

Thanks for opening this pull request!

• ❌ Please link an issue that describes the reason for this pull request, otherwise your pull request will be closed. Make sure to write it as Closes: #123 in the PR description, so I can recognize it.

[parseplatformorg]

🎉 This change has been released in version 2.4.0