Fix fmt in decoder.rs

Signed-off-by: Jiahao XU <[email protected]>

Author: NobodyXu

src/futures/write/generic/decoder.rs

@@ -88,9 +88,7 @@ impl<W: AsyncWrite, D: Decode> Decoder<W, D> {
                 }
 
                 State::Done => {
-                    return Poll::Ready(Err(io::Error::other(
-                        "Write after end of stream",
-                    )))
+                    return Poll::Ready(Err(io::Error::other("Write after end of stream")))
                 }
             };