Fix deprecation issues for PHP CS Fixer

[ttomdewit]

Summary

As per #37 we caught some deprecations in PHP CS Fixer, this PR aims to solve them.

Explanation

Ran the following commands:

1. docker run --rm -v "$(pwd):/app" -w /app composer:2 install
2. docker run --rm -v "$(pwd):/app" -w /app composer:2 fix
3. docker run --rm -v "$(pwd):/app" -w /app composer:2 type
4. docker run --rm -v "$(pwd):/app" -w /app composer:2 test

All were fine.

Checklist

• I have provided a summary and an explanation
• I have reviewed the PR myself and left comments to provide context
• I have covered the changes with tests as appropriate - N/A
• I have made sure static analysis and other checks are successful

[osteel]

Thanks for doing the maintenance tasks for me! Love it haha