alpaca_sft.prompt problem

An extra space on the last line of the `prompt` file in `alpaca_sft.prompt` caused the `test_packed_sft_dataset` test case to fail regardless. I have already resolved this issue, and I hope you can fix it as well.

<img width="2025" height="1286" alt="Image" src="https://github.com/user-attachments/assets/a37edd5e-627d-4f92-8aa2-51877185de93" />