Updated workbook to use GPT-4o-mini

[phundal-openai]

Also smoothed out some of the prompt examples to better represent what was trying to be acomplished

Summary

Briefly describe the changes and the goal of this PR. Make sure the PR title summarizes the changes effectively.

Motivation

Why are these changes necessary? How do they improve the cookbook?

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[msingh-openai]

Thanks for updating the model!