Remove GP 0.6.7 support

[tomusdrw]

• Clean up https://github.com/FluffyLabs/test-vectors
• Migrate javajam traces to 0.7.1: https://github.com/javajamio/javajam-trace/tree/main

[tomusdrw]

This is partially done in #809 CC @DrEverr please consider also clearing the test-vectors repo and using newer javajam traces.

[DrEverr]

Cleaned up in FluffyLabs/test-vectors#27