message: Use match for `Frame::is_allowed`
  The original implementation of this had more complicated logic, but the
  spec has since gotten cleaner.  So the code can be too.
diff: @@ -530,15 +530,16 @@ impl Frame {
  }
  pub fn is_allowed(&self, pt: PacketType) -> bool {
  - if matches!(self, Self::Padding | Self::Ping) {
  - true
  - } else if matches!(self, Self::Crypto {..} | Self::Ack {..} | Self::ConnectionClose { error_code: CloseError::Transport(_), .. })
  - {
  - pt != PacketType::ZeroRtt
  - } else if matches!(self, Self::NewToken {..} | Self::ConnectionClose {..}) {
  - pt == PacketType::Short
  - } else {
  - pt == PacketType::ZeroRtt || pt == PacketType::Short
  + match self {
  + Self::Padding | Self::Ping => true,
  + Self::Crypto { .. }
  + | Self::Ack { .. }
  + | Self::ConnectionClose {
  + error_code: CloseError::Transport(_),
  + ..
  + } => pt != PacketType::ZeroRtt,
  + Self::NewToken { .. } | Self::ConnectionClose { .. } => pt == PacketType::Short,
  + _ => pt == PacketType::ZeroRtt || pt == PacketType::Short,
  }
  }
  