Fix prompt tuning sampling error when LIMIT is greater than number of…

[billierinaldi]

Description

Prompt tuning errors out when the number of chunks is less than the default LIMIT, saying "Auto-prompt generation failed: Cannot take a larger sample than population when 'replace=False'"

Proposed Changes

This patch sets the limit to the min of LIMIT and the number of chunks.

Checklist

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