Add time stamp for GA test

[charlesli640]

Description

Add time stamp for analysis of b/496210310

Tests

python3 -m pytest -v tests/integration/gradient_accumulation_test.py::GradientAccumulationTest::test_grad_accumulate_same_loss

Checklist

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• I have performed a self-review of my code. For an optional AI review, add the gemini-review label.
• I have necessary comments in my code, particularly in hard-to-understand areas.
• I have run end-to-end tests tests and provided workload links above if applicable.
• I have made or will make corresponding changes to the doc if needed, including adding new documentation pages to the relevant Table of Contents (toctree directive) as explained in our documentation.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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