change sft train and sft.yml path

[susanbao]

Description

Move the sft.yml path from src/MaxText/configs to src/maxtext/configs/post_train. In the #3044, maxText move all config files from src/MaxText/configs to src/maxtext/configs. We need to modify the sft.yml path for this.

XLML DAGs failed for using src/maxtext/configs/sft.yml, error:

FileNotFoundError: [Errno 2] No such file or directory: '/deps/src/maxtext/configs/sft.yml'

FIXES:b/483253279

Tests

Trigger the XLML DAG for jax_ai_image_tpu_e2e to test

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[shuningjin]

Thanks for the fix!