Fix: audio and octet stream response

[VisargD]

There are 2 issues with gateway's audio and octet-stream resonse forwarding.

• For audio response, it has a hardcoded audio/mpeg content-type check. But OpenAI sends some other audio content types also. Example: audio/aac, audio/flac, etc. Due to the hardcoded check, the other types goes to JSON response handler instead of audio response handler
  

  gateway/src/handlers/handlerUtils.ts

  Lines 522 to 524 in 33b1122

  	} else if (responseContentType === CONTENT_TYPES.AUDIO_MPEG) {
  	return handleAudioResponse(response)
  	} else if (responseContentType === CONTENT_TYPES.APPLICATION_OCTET_STREAM) {

• In handleAudioResponse function, JSON.stringifiy(response.body) is not required to forward the response as it is. JSON.stringify needs to be removed
  

  gateway/src/handlers/streamHandler.ts

  Lines 73 to 75 in 33b1122

  	export async function handleAudioResponse(response: Response) {
  	return new Response(JSON.stringify(response.body), response);
  	}

• In handleOctetStreamResponse function, JSON.stringifiy(response.body) is not required to forward the response as it is. JSON.stringify needs to be removed
  

  gateway/src/handlers/streamHandler.ts

  Lines 77 to 79 in 33b1122

  	export async function handleOctetStreamResponse(response: Response) {
  	return new Response(JSON.stringify(response.body), response);
  	}