Syntax highlighting of server-protocol/Packet_0xA9

# Packet 0xA9

Clients send Packet 0xA9 to inform the server that they've backed out of the Quest Select menu for whatever reason.

## Dreamcast Packet Format
| Bytes | Meaning |
| --- | --- |
| 0x00 | Packet Type (0xA9) |
| 0x01 | Flags (0x00) |
| 0x02-0x03 | Packet Size (0x04) |