chore: support python 3.12

[ikrommyd]

Support Python 3.12 with newest zfit release

Checklist

• change approved
• implementation finished
• correct namespace imported
• tests added
• CHANGELOG updated

[jonas-eschle]

Looks good!

[jonas-eschle]

Can be merged from my side! After the merge, we can make a release. Familiar with it?
The cd (it .github/cd.yml) triggers the deployment phase if a release has been made on GH. Making a release is best in conjunction with a tag, i.e. you can create a release and tag on github, or create a release (adjust the changelog accordingly) and then make a release here. This should trigger pypi deployment.

A step-by-step guide is here: https://github.com/zfit/zfit-development/wiki/Release-strategy

[jonas-eschle]

Feel free to make a new release, if you have questions, just ask, otherwise just go ahead and I am looking forward for the next (0.7.0) release out ;)