CI: Update to cibuildwheel 2.20.0
[cibuildwheel](https://github.com/pypa/cibuildwheel) [2.20.0](https://github.com/pypa/cibuildwheel/releases/tag/v2.20.0) uses the ABI stable Python 3.13.0rc1 and build Python 3.13 wheels by default, which allows removing the `CIBW_PRERELEASE_PYTHONS` flag.
About 80 of these types of errors happen, on Python 3.13 only:
      
```
  >       assert isinstance(left, ExtensionArray), "left is not an ExtensionArray"
  E       AssertionError: left is not an ExtensionArray
```
Any idea what causes these? It seems similar errors are [going on](https://github.com/pandas-dev/pandas/actions/workflows/wheels.yml?query=branch%3Amain) on the main branch ([example](https://github.com/pandas-dev/pandas/actions/runs/10242118536/job/28331368285)).

Edit: It seems this was the [last passing wheel build](https://github.com/pandas-dev/pandas/actions/runs/10105253109), which ran on July 26th. It did include successful Python 3.13 wheel builds.

So the errors are probably unrelated to this PR. Thanks @EwoutH  Backported in https://github.com/pandas-dev/pandas/pull/59835