message: refactor(http2): fix unstable name clash of Cursor::remaining
diff: @@ -255,7 +255,7 @@ impl<B: Buf> Buf for SendBuf<B> {
  fn remaining(&self) -> usize {
  match *self {
  Self::Buf(ref b) => b.remaining(),
  - Self::Cursor(ref c) => c.remaining(),
  + Self::Cursor(ref c) => Buf::remaining(c),
  Self::None => 0,
  }
  }
  