Remove unused dependencies: futures-intrusive (#279)

Author: fanatid

Cargo.toml

@@ -34,7 +34,6 @@ chrono = "0.4.7"
 derivative = "2.1.1"
 err-derive = "0.2.3"
 futures = "0.3.5"
-futures-intrusive = "0.3.0"
 hex = "0.4.0"
 hmac = "~0.7.1"
 lazy_static = "1.4.0"