Updating Discrete choice issue to fix parameter identification issue

[NathanielF]

Better handling of parameter identification in Discrete choice model

Adding a fix for parameter identification in the discrete choice notebook

Related to this issue and the PyMC discourse discussion:
https://discourse.pymc.io/t/inconsistencies-w-r-in-discrete-choice-and-random-utility-pymc-example/16488/4

#780

and older discussion here: #617

• Notebook follows style guide https://docs.pymc.io/en/latest/contributing/jupyter_style.html
• PR description contains a link to the relevant issue:
  • a tracker one for existing notebooks (tracker issues have the "tracker id" label)
  • or a proposal one for new notebooks
• Check the notebook is not excluded from any pre-commit check: https://github.com/pymc-devs/pymc-examples/blob/main/.pre-commit-config.yaml

Helpful links

• https://github.com/pymc-devs/pymc-examples/blob/main/CONTRIBUTING.md

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📚 Documentation preview 📚: https://pymc-examples--781.org.readthedocs.build/en/781/

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[NathanielF]

A relatively small change to fix the issue above. Tagging @drbenvincent as it's of interest from the causal inference pov and @OriolAbril because i think you reviewed the original PR.

[NathanielF]

Thanks so much @juanitorduz it's a small change but very important for these models! Would you be able to merge it for me, i don't think i have permissions for that on this repo.