fix(genai): update virtual-try-on model to stable version virtual-try-on-001

[angelcaamal]

Description

Fixes Internal: b/505833340

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Checklist

• I have followed guidelines from CONTRIBUTING.MD and Samples Style Guide
• Tests pass: npm test (see Testing)
• Lint pass: npm run lint (see Style)
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• Please merge this PR for me once it is approved

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[gemini-code-assist]

Code Review

This pull request updates the model identifier in the virtualTryOn function from 'virtual-try-on-preview-08-04' to 'virtual-try-on-001'. I have no feedback to provide as there are no review comments to evaluate.