examples(foundational): use system_instruction in all examples

examples/foundational/34-audio-recording.py

@@ -115,19 +115,16 @@ async def run_bot(transport: BaseTransport, runner_args: RunnerArguments):
         voice_id="71a7ad14-091c-4e8e-a314-022ece01c121",
     )
 
-    llm = OpenAILLMService(api_key=os.getenv("OPENAI_API_KEY"), model="gpt-4")
+    llm = OpenAILLMService(
+        api_key=os.getenv("OPENAI_API_KEY"),
+        model="gpt-4",
+        system_instruction="You are a helpful assistant demonstrating audio recording capabilities. Keep your responses brief and clear.",
+    )
 
     # Create audio buffer processor
     audiobuffer = AudioBufferProcessor()
 
-    messages = [
-        {
-            "role": "system",
-            "content": "You are a helpful assistant demonstrating audio recording capabilities. Keep your responses brief and clear.",
-        },
-    ]
-
-    context = LLMContext(messages)
+    context = LLMContext()
     user_aggregator, assistant_aggregator = LLMContextAggregatorPair(
         context,
         user_params=LLMUserAggregatorParams(vad_analyzer=SileroVADAnalyzer()),