refactor(meeting-bot): inline audio fallback guard (#129975)

Amp-Thread-ID: https://ampcode.com/threads/T-01a037b7-6475-7130-8be6-39147410914b

Co-authored-by: Amp <amp@ampcode.com>

src/meeting-bot/realtime-audio-format.ts

@@ -82,10 +82,7 @@ function decodeMeetingTelephonyTtsAudio(
     case "alaw":
       return alawToPcm(audio);
   }
-  return unsupportedMeetingTelephonyTtsFormat(sourceFormat);
-}
-
-function unsupportedMeetingTelephonyTtsFormat(_format: never): never {
+  sourceFormat satisfies never;
   throw new Error("Unsupported telephony TTS output format for meeting platform");
 }