transport(livekit): force specifying a vad analyzer

Don't default to SileroVADAnalyzer(). Also, resample to input sample rate.

examples/foundational/01b-livekit-audio.py

@@ -4,9 +4,6 @@ import os
 import sys
 
 import aiohttp
-from dotenv import load_dotenv
-from livekit import api  # pip install livekit-api
-from loguru import logger
 
 from pipecat.frames.frames import TextFrame
 from pipecat.pipeline.pipeline import Pipeline
@@ -15,6 +12,12 @@ from pipecat.pipeline.task import PipelineTask
 from pipecat.services.cartesia import CartesiaTTSService
 from pipecat.transports.services.livekit import LiveKitParams, LiveKitTransport
 
+from livekit import api
+
+from loguru import logger
+
+from dotenv import load_dotenv
+
 load_dotenv(override=True)
 
 logger.remove(0)