fixup! Re-design the StreamMuxer trait

Use `Bytes::new` to reduce diff and properly format bounds.

muxers/mplex/src/lib.rs

@@ -190,8 +190,8 @@ where
 
 /// Active substream to the remote.
 pub struct Substream<C>
-    where
-        C: AsyncRead + AsyncWrite + Unpin,
+where
+    C: AsyncRead + AsyncWrite + Unpin,
 {
     /// The unique, local identifier of the substream.
     id: LocalStreamId,
@@ -202,13 +202,13 @@ pub struct Substream<C>
 }
 
 impl<C> Substream<C>
-    where
-        C: AsyncRead + AsyncWrite + Unpin,
+where
+    C: AsyncRead + AsyncWrite + Unpin,
 {
     fn new(id: LocalStreamId, io: Arc<Mutex<io::Multiplexed<C>>>) -> Self {
         Self {
             id,
-            current_data: Bytes::default(),
+            current_data: Bytes::new(),
             io,
         }
     }