examples: use task.cancel() when participant leaves or disconnects

examples/foundational/07e-interruptible-playht-http.py

@@ -14,14 +14,12 @@ from loguru import logger
 from runner import configure
 
 from pipecat.audio.vad.silero import SileroVADAnalyzer
-from pipecat.frames.frames import EndFrame
 from pipecat.pipeline.pipeline import Pipeline
 from pipecat.pipeline.runner import PipelineRunner
 from pipecat.pipeline.task import PipelineParams, PipelineTask
 from pipecat.processors.aggregators.openai_llm_context import OpenAILLMContext
 from pipecat.services.openai import OpenAILLMService
 from pipecat.services.playht import PlayHTHttpTTSService
-from pipecat.transcriptions.language import Language
 from pipecat.transports.services.daily import DailyParams, DailyTransport
 
 load_dotenv(override=True)
@@ -94,7 +92,7 @@ async def main():
 
         @transport.event_handler("on_participant_left")
         async def on_participant_left(transport, participant, reason):
-            await task.queue_frame(EndFrame())
+            await task.cancel()
 
         runner = PipelineRunner()