misc/py-instructor: update to 0.6.8

Changelog:

• https://github.com/jxnl/instructor/releases/tag/0.5.0
• https://github.com/jxnl/instructor/releases/tag/0.5.1
• https://github.com/jxnl/instructor/releases/tag/0.5.2
• https://github.com/jxnl/instructor/releases/tag/0.6.0
• https://github.com/jxnl/instructor/releases/tag/0.6.1
• https://github.com/jxnl/instructor/releases/tag/0.6.2
• https://github.com/jxnl/instructor/releases/tag/0.6.3
• https://github.com/jxnl/instructor/releases/tag/0.6.4
• https://github.com/jxnl/instructor/releases/tag/0.6.5
• https://github.com/jxnl/instructor/releases/tag/0.6.6
• https://github.com/jxnl/instructor/releases/tag/0.6.7
• https://github.com/jxnl/instructor/releases/tag/0.6.8

Reported by: portscout