Update auto_prompt_tuning.md

[JackyYangPassion]

Description

fix document bug

Related Issues

[Reference any related issues or tasks that this pull request addresses.]

Proposed Changes

This step is optional, though is is highly encouraged to run it as it will yield better results when executing an Index Run

This step is optional, though it is highly encouraged to run it as it will yield better results when executing an Index Run

Checklist

• [ ] I have tested these changes locally.
• [ ] I have reviewed the code changes.
• [ ] I have updated the documentation (if necessary).
• [ ] I have added appropriate unit tests (if applicable).

Additional Notes

[Add any additional notes or context that may be helpful for the reviewer(s).]