`newThread.fetchStarterMessage` failing for some threads

### Describe the bug

a failing GET call was noticed in the logs for URL's such as
```
https://discord.com/api/v10/channels/1101313474962927617/messages/1101313474962927617
```

Tracing this back, it appears the fetch for the thread's starter message is failing:
https://github.com/aws-amplify/discord-bot/blob/main/src/lib/discord/client.ts#L386