Fix Rector job on PR to main repository

[rene-bos]

Run only on PR's from branches on main repository (from core contributors), not on the forks or PR's from forks.

[driftingly]

I might have merged this too early. Sorry!

[rene-bos]

No problem! It should have created it as draft if I did not wanted it to get merged. Its fine to be merged I think. If TomasVotruba agrees to move the check to rector.yaml we can just remove the if-statement.

For now we can keep the change here, as it will avoid errors like we had on #82.

[driftingly]

Should we revert 3f57062

[rene-bos]

Yeah that's a good one. When we don't fix it it will pop up in a totally unrelated pull request some time 😉 Because of some strange hickup the change has already been committed to #82 ([ci-review] Rector Rectify).

Do you have time to check #82 and maybe create a release afterwards? At my company (Visma) we would love to have that change 😄. Avoids pinning to our fork and the associated maintenance of it. Sorry for making your day busy with all that PR's 😉