Update example to use Claude Sonnet 3.5

[huythngo]

Update example to use Claude Sonnet 3.5

Fixes #b/b346581004

Note: Before submitting a pull request, please open an issue for discussion if you are not associated with Google.

Checklist

• [ ] I have followed Sample Guidelines from AUTHORING_GUIDE.MD
• [ ] README is updated to include all relevant information
• [ ] Tests pass: nox -s py-3.9 (see Test Environment Setup)
• [ ] Lint pass: nox -s lint (see Test Environment Setup)
• [ ] These samples need a new API enabled in testing projects to pass (let us know which ones)
• [ ] These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• [ ] This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample
• [ ] This sample adds a new Product API, and I updated the Blunderbuss issue/PR auto-assigner with the codeowners for this sample
• [ ] Please merge this PR for me once it is approved

[huythngo]

/gcbrun

[gericdong]

Test errors in Python 3.8 are fixed in #11858 Test errors in Python 3.11 are fixed in #11875

[huythngo]

/gcbrun

[huythngo]

/gcbrun

[huythngo]

/gcbrun