[BFCL Dataset Revamp 4/n] Multi-Turn (Part 2)

[Fanjia-Yan]

This PR continues #737 a 2-week initiative to re-scrutinize across V3 dataset issues with several objectives:

• Eliminate Ground Truth mismatches against user questions.
• Polish ambiguous prompts that have unclear user intents to eliminate biased-judgement and saturation.

Following PRs will be rolled out on a daily basis by categories.

This PR cleaned multi_turn_base from 30-60 entry

Note: #733 is a pre-requisite for this PR to merge.