Run CI codestyle fixes on PRs rather than master

[jnoordsij]

The current CI configuration tries to commit automatic style fixes to the master branch. This fails due to pushing not being allowed due to branch protection rules; see e.g. https://github.com/barryvdh/laravel-debugbar/actions/runs/9922834440/job/27412338699#step:7:62.

This PR moves the codestyle fixes to be applied on the individual PRs. Alternatively, the protection rules could be updated to ensure the GitHub actions bot is allowed to push to the master branch.

Edit: appearently the config suggested per https://github.com/stefanzweifel/git-auto-commit-action?tab=readme-ov-file#checkout-the-correct-branch does not seem to work yet with checking out; might investigate later.