Gemma chat notebook update: add Gemma 2 model info

[joefernandez]

Description of the change

Gemma chat notebook update: add Gemma 2 model info

Motivation

Launch of Gemma 2 models

Type of change

Choose one: Documentation

Checklist

• [x ] I have performed a self-review of my code.
• [x ] I have added detailed comments to my code where applicable.
• [x ] I have verified that my change does not break existing code.
• [x ] My PR is based on the latest changes of the main branch (if unsure, please run git pull --rebase upstream main).
• [x ] I am familiar with the Google Style Guide for the language I have coded in.
• [x ] I have read through the Contributing Guide and signed the Contributor License Agreement.

[review-notebook-app]

Check out this pull request on 

See visual diffs & provide feedback on Jupyter Notebooks.

---

Powered by ReviewNB