You can check out the release notes here. Consensus hasn't changed, the latest upgrade is just for P2P stability. This is specifically best for seed nodes, which create the P2P "spine" of the network, connecting the whole ecosystem together. Witness nodes are more of the "brain".
In my case, my witness isn't directly accessible via incoming P2P or even SSH connections. It's locked out. So while I could upgrade, it has zero effect and I see no need to reboot.
you can read more about it here. In this, he says,I know at least one other witness @gtg has a similar set up,
Your witness node connects ONLY to your seed nodes using VLAN or another private, low latency network solution of your choice. All other incoming/outgoing connections should be blocked except for the secure shell, preferably limited to access only from your IPs.
Upgrades that change consensus will of course be necessary -- but this one isn't about that. As @ausbitbank says, there's a lot more to this role than just upgrading software. ;)