Remove #[allow(clippy::useless_attribute)]

Author: taiki-e

futures-io/src/lib.rs

@@ -27,7 +27,6 @@ mod if_std {
 
     // Re-export some types from `std::io` so that users don't have to deal
     // with conflicts when `use`ing `futures::io` and `std::io`.
-    #[allow(clippy::useless_attribute)] // https://github.com/rust-lang/rust-clippy/issues/4106
     #[allow(unreachable_pub)] // https://github.com/rust-lang/rust/issues/57411
     pub use self::StdIo::{
         Error as Error,

futures-util/src/compat/compat01as03.rs

@@ -12,7 +12,6 @@ use std::task::Context;
 use futures_sink::Sink as Sink03;
 
 #[cfg(feature = "io-compat")]
-#[allow(clippy::useless_attribute)] // https://github.com/rust-lang/rust-clippy/issues/4106
 #[allow(unreachable_pub)] // https://github.com/rust-lang/rust/issues/57411
 pub use io::{AsyncRead01CompatExt, AsyncWrite01CompatExt};