Fix missing futures-util feature

The issue is actually in actix 0.10.0

Cargo.toml

@@ -22,7 +22,7 @@ serde = { version = "1.0.116", features = ["derive"] }
 serde_json = "1.0.57"
 actix = { version = "0.10.0", default-features = false }
 actix-rt = "1.1.1"
-futures-util = { version = "0.3.5", default-features = false, features = ["std", "async-await"] }
+futures-util = { version = "0.3.5", default-features = false, features = ["std", "async-await", "sink"] }
 num-traits = "0.2.12"
 num-derive = "0.3.2"