[5.2] Update phpstan to 2.0

[Hackwar]

Summary of Changes

phpstan 2.0 has been released: https://phpstan.org/blog/phpstan-2-0-released-level-10-elephpants This PR updates our repo to version 2.0.

Testing Instructions

Codereview

Link to documentations

Please select:

• [ ] Documentation link for docs.joomla.org:

• [X] No documentation changes for docs.joomla.org needed

• [ ] Pull Request link for manual.joomla.org:

• [X] No documentation changes for manual.joomla.org needed

[richard67]

I've reviewed the PR and have compared the phpstan logs from Drone from this PR with the log from another PR. Phpstan works as well as before.

[richard67]

Thanks.