Constant libp2p_rendezvous::MAX_TTL

pub const MAX_TTL: Ttl = 60 * 60 * 72; // 0x0000_0000_0003_f480u64

By default, nodes should allow a maximum TTL of 72h

https://github.com/libp2p/specs/tree/master/rendezvous#recommendations-for-rendezvous-points-configurations.