Fix Service<u8> request documentation
@@ -77,7 +77,7 @@ use self::ready::{err, ok, ready, Ready};
///
/// fn poll_ready(&self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> { ... }
///
-/// fn call(&self, req: Self::Request) -> Self::Future { ... }
+/// fn call(&self, req: u8) -> Self::Future { ... }
/// }
/// ```
///
