Update to criterion 0.4

Author: sdroege

Cargo.toml

@@ -42,7 +42,7 @@ winapi = { version = "0.3.9", features = ["winsock2"] }
 async-channel = "1"
 async-net = "1"
 blocking = "1"
-criterion = "0.3.6"
+criterion = "0.4"
 getrandom = "0.2.7"
 signal-hook = "0.3"
 tempfile = "3"