"Press Enter to Reconnect" is not appropriate when using --once

[DannyBen]

Describe the bug

In previous versions, the message that appears on exit made more sense. It used to be "Connection Closed" - which was more appropriate for my use cases.

I think it should be reverted to this message, if not for all cases, at least when running with --once.

To Reproduce

1. Run ttyd --once --port 3000 --readonly echo PONG
2. Open the browser at http://localhost:3000
3. See PONG followed by "Press Enter to Reconnect"

Expected behavior

See "Connection Closed" as the exit message.

Environment:

• OS: Ubuntu 20.04 LTS
• Browser: Chrome

[tsl0922]

Thanks, will change the message for --once for the next release.