Update tokio to 1.40 (#1611)

Keep in sync with Omicron and Propolis (who now both have this)

Co-authored-by: Alan Hanson <alan@oxide.computer>

Author: leftwo

Cargo.lock

@@ -101,7 +101,7 @@ strum_macros = "0.26"
 tempfile = "3"
 test-strategy = "0.4.0"
 thiserror = "1"
-tokio = { version = "1.36", features = ["full"] }
+tokio = { version = "1.40", features = ["full"] }
 tokio-rustls = { version = "0.24.1" }
 tokio-test = "*"
 tokio-util = { version = "0.7", features = ["codec"]}