message: Minor fix to RtpPacket::ToString.
  Cr-Commit-Position: refs/heads/main@{#38046}
diff: @@ -685,7 +685,7 @@ bool RtpPacket::RemoveExtension(ExtensionType type) {
  std::string RtpPacket::ToString() const {
  rtc::StringBuilder result;
  - result << "{payload_type=" << payload_type_ << "marker=" << marker_
  + result << "{payload_type=" << payload_type_ << ", marker=" << marker_
  << ", sequence_number=" << sequence_number_
  << ", padding_size=" << padding_size_ << ", timestamp=" << timestamp_
  << ", ssrc=" << ssrc_ << ", payload_offset=" << payload_offset_
  