[vertexai] Use json of unary-success-citations

[rlazo]

The test files have been updated to include json extension versions of the tests files. The old, txt extension files are deprecated and will be deleted eventually.

[changeset-bot]

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Latest commit: 8479960

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[google-oss-bot]

Size Report ¹

Affected Products

No changes between base commit (475c81a) and merge commit (fe5dd5b).

Test Logs

• Base (475c81a): https://github.com/firebase/firebase-js-sdk/actions/runs/14621865614
• Merge (fe5dd5b): https://github.com/firebase/firebase-js-sdk/actions/runs/14723319642

1. https://storage.googleapis.com/firebase-sdk-metric-reports/tFLZcw5CBX.html

[google-oss-bot]

Size Analysis Report ¹

Affected Products

No changes between base commit (475c81a) and merge commit (fe5dd5b).

Test Logs

• Base (475c81a): https://github.com/firebase/firebase-js-sdk/actions/runs/14621865614
• Merge (fe5dd5b): https://github.com/firebase/firebase-js-sdk/actions/runs/14723319642

1. https://storage.googleapis.com/firebase-sdk-metric-reports/MMO77yhTE9.html