chore(genai): replace deprecated genai image generation model

[alarconesparza]

Description

Fixes internal
b/505834660
b/507049205

Checklist

• I have followed Sample Format Guide
• pom.xml parent set to latest shared-configuration
• Appropriate changes to README are included in PR
• 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)
• Tests pass: mvn clean verify required
• Lint passes: mvn -P lint checkstyle:check required
• Static Analysis: mvn -P lint clean compile pmd:cpd-check spotbugs:check advisory only
• 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

[gemini-code-assist]

Code Review

This pull request updates the virtual try-on model ID to 'virtual-try-on-001' in the sample code and integration tests. It also removes the test scope for the 'google-cloud-storage' dependency in the pom.xml. A review comment points out that this dependency should remain in the test scope to avoid unnecessary compile-time dependencies and a larger artifact footprint.

[XrossFox]

It seems that these constant no longer is being used anywhere, since the code line that used it, now points to the general availability model. Since it's not longer needed, line 40 should be removed (or either, line 85, returned to point to the preview model).