style(lib): address most clippy lints

src/body/payload.rs

@@ -33,9 +33,8 @@ pub trait Payload: sealed::Sealed + Send + 'static {
     /// Note: Trailers aren't currently used for HTTP/1, only for HTTP/2.
     fn poll_trailers(
         self: Pin<&mut Self>,
-        cx: &mut task::Context<'_>,
+        _cx: &mut task::Context<'_>,
     ) -> Poll<Result<Option<HeaderMap>, Self::Error>> {
-        drop(cx);
         Poll::Ready(Ok(None))
     }