Update PlayHT to use the latest Websocket connection endpoint

[markbackman]

Please describe the changes in your PR. If it is addressing an issue, please reference that as well.

Updating to support the latest Websocket API from PlayHT: https://docs.play.ht/reference/playht-tts-websocket-api. This new endpoint also appears to solve the missing audio issue where sentences wouldn't be spoken.

Service changes impacting this PR:

1. Websocket URL:

When you make a POST request to /api/v4/websocket-auth, you get back a response like this:
jsonCopy{
  "websocket_urls": {
    "Play3.0-mini": "wss://ws.fal.run/playht-fal/playht-tts/ws?fal_jwt_token=<token1>",
    "PlayDialog": "wss://ws.fal.run/playht-fal/playht-tts-ldm/ws?fal_jwt_token=<token2>",
    "PlayDialogMultilingual": "wss://ws.fal.run/playht-fal/playht-tts-multilingual-ldm/ws?fal_jwt_token=<token3>"
  },
  "expires_at": "2024-12-11T22:17:37.429Z"
}

We need to get the wss URL from the response.

2. Also, they now include start and end messages:

For each request, receive, in order, a {"type":"start"} message, followed by audio output as binary messages, and a {"type":"end"} as indicator of end of request.

[aconchillo]

Nice! LGTM