Update dependencies to PHP 8.5 and Symfony 8.1

[javiereguiluz]

This is the same as #53 but with a new PR to see if we can unstuck GitHubo this one.

[stof]

You also need to update the CI tooling (defined in vendor-bin/ to resolve dependencies separately) to make them use versions that are compatible with PHP 8.5 instead of old versions.