chore: use ready macro from futures-core (#1300)

tokio-sync/src/lib.rs

@@ -21,19 +21,6 @@ macro_rules! debug {
     }
 }
 
-/// Unwrap a ready value or propagate `Poll::Pending`.
-#[macro_export]
-macro_rules! ready {
-    ($e:expr) => {{
-        use std::task::Poll::{Pending, Ready};
-
-        match $e {
-            Ready(v) => v,
-            Pending => return Pending,
-        }
-    }};
-}
-
 macro_rules! if_fuzz {
     ($($t:tt)*) => {{
         if false { $($t)* }