fix sequence diagram lines

[alixander]

shape: sequence_diagram

client: Client Server
reverst: Reverst Tunnel
user: End User

registration handshake: {
  client -> reverst.handshake: RegisterListenerRequest
  reverst.handshake -> client: RegisterListenerResponse
}

tunnelled request: {
  user -> reverst.req: Request
  reverst -> client.req: Request
  client.req -> reverst: Response
  reverst.req -> user: Response
}

source