Update readme example

[kiramclean]

Updates the example added to the readme to be complete and show the correct example output.

Description

This PR updates the example previously added to the readme in https://github.com/pymc-devs/pymc/pull/7281/commits/b2e5c1e84dfe2a8b4e71583bec8845a599aa4ad5 with the correct output.

Related Issue

• [x] Closes https://github.com/pymc-devs/pymc/issues/7267
• [ ] Related to #

Checklist

• [x] Checked that the pre-commit linting/style checks pass
• [ ] Included tests that prove the fix is effective or that the new feature works
• [x] Added necessary documentation (docstrings and/or example notebooks)
• [ ] If you are a pro: each commit corresponds to a relevant logical change

Type of change

• [ ] New feature / enhancement
• [ ] Bug fix
• [x] Documentation
• [ ] Maintenance
• [ ] Other (please specify):

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📚 Documentation preview 📚: https://pymc--7358.org.readthedocs.build/en/7358/

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