chore: support tokio 1.33 without stats feature (#55)

Cargo.toml

@@ -22,7 +22,7 @@ rt = ["tokio"]
 tokio-stream = "0.1.11"
 futures-util = "0.3.19"
 pin-project-lite = "0.2.7"
-tokio = { version = "1.31.0", features = ["rt", "stats", "time", "net"], optional = true }
+tokio = { version = "1.31.0", features = ["rt", "time", "net"], optional = true }
 
 [dev-dependencies]
 axum = "0.6"
@@ -47,4 +47,4 @@ all-features = true
 rustdoc-args = ["--cfg", "docsrs", "--cfg", "tokio_unstable"]
 # it's necessary to _also_ pass `--cfg tokio_unstable` to rustc, or else
 # dependencies will not be enabled, and the docs build will fail.
-rustc-args = ["--cfg", "tokio_unstable"]
+rustc-args = ["--cfg", "tokio_unstable"]