revert of #2658

[dimapihtar]

What does this PR do ?

Reverts #2658

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[dimapihtar]

/ok to test cfe9bf6

[sbak5]

/claude review

[svcnvidia-nemo-ci]

🔄 Merge queue validation started!

You can track the progress here: https://github.com/NVIDIA/Megatron-LM/actions/runs/22867194032

[claude]

LGTM — clean revert of #2658, restoring the original RNG sharding by PP/TP only.