Update Orbax to 0.12.2 (Pathways Multi-Tiered Checkpointing Support)

[SujeethJinesh]

Description

Update Orbax with latest version that supports MTC on Pathways. Followed instructions here

FIXES: b/541298927

Tests

Internal testing on Orbax candidate.

Checklist

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• 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.

[gemini-code-assist]

Caution

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[gemini-code-assist]

Caution

The consumer version of Gemini Code Assist on GitHub has been sunset. All code review activity has officially ceased.

[DmitryKakurin]

I can only LGTM this change: orbax-checkpoint>=0.12.2
Please find approvers for other version changes.