go/neo/proto: Version 4 -> 5

This protocol version corresponds to protocol version used by NEO/py
v1.11 and was set in NEO/py commit 9a5b46dd (Bump protocol version).

The protocol definition was updated to match that NEO/py release in
the previous patch.

go/neo/proto/proto.go

@@ -81,7 +81,7 @@ const (
 	// The protocol version must be increased whenever upgrading a node may require
 	// to upgrade other nodes. It is encoded as a 4-bytes big-endian integer and
 	// the high order byte 0 is different from TLS Handshake (0x16).
-	Version = 4
+	Version = 5
 
 	// length of packet header
 	PktHeaderLen = 10 // = unsafe.Sizeof(PktHeader{}), but latter gives typed constant (uintptr)