Fix end_of_turn_confidence_threshold: set to 1.0 (not 0.0) for universal-streaming

- u3-rt-pro: Does not set parameter (not used)
- universal-streaming models: Set to 1.0 to maintain fast response
- This ensures fast response time matches previous implementation

src/pipecat/services/assemblyai/stt.py

@@ -267,7 +267,7 @@ class AssemblyAISTTService(WebsocketSTTService):
         else:
             # universal-streaming: Different configuration (works differently)
             updates = {
-                "end_of_turn_confidence_threshold": 0.0,
+                "end_of_turn_confidence_threshold": 1.0,
                 "min_turn_silence": 160,
             }