Use std::task::ready instead of ready_polyfill::ready

The `std::task::ready` macro has been available since Rust 1.64 now.
Our MSRV is 1.70 currently, so we can use it.

src/inject.rs

@@ -1,11 +1,11 @@
-use std::{future::Future, task::Poll};
+use std::{future::Future, task::{ready, Poll}};
 
 use bytes::{Buf, Bytes};
 use http::{header, Request, Response};
 use http_body::Frame;
 use tower::Service;
 
-use crate::{predicate::Predicate, ready_polyfill::ready};
+use crate::predicate::Predicate;
 
 #[derive(Clone, Debug)]
 pub struct InjectService<S, ReqPred, ResPred> {

src/lib.rs

@@ -80,7 +80,6 @@ mod inject;
 mod long_poll;
 mod overlay;
 pub mod predicate;
-mod ready_polyfill;
 
 use std::{convert::Infallible, time::Duration};