net/yggdrasil: Update to 0.5.6

ChangeLog: https://github.com/yggdrasil-network/yggdrasil-go/releases/tag/v0.5.6

Go 1.21 is now required to build Yggdrasil

Added

*The getPeers endpoint now reports the RTT/latency of directly connected peers

Changed

• The tree parent selection algorithm now prefers the lowest latency peers instead of the most stable
• Session key exchange logic has been changed to improve throughput and reduce occasional jitter

Fixed

• Bloom filter hashing now works correctly on big-endian architectures
• Incorrect buffer pool usage has been fixed, reducing memory allocations
• The multicast beacon interval now backs off correctly, reducing the number of beacons sent
• A denial-of-service vulnerability in the QUIC library has been fixed with a dependency update

PR: 279433
Reported by: freebsd@neilalexander.dev (maintainer)