re-export TurnDetection for xAI (#4306)

Author: tinalenguyen

livekit-plugins/livekit-plugins-xai/livekit/plugins/xai/realtime/__init__.py

@@ -1,3 +1,5 @@
+from openai.types.beta.realtime.session import TurnDetection
+
 from livekit.plugins.openai.realtime import RealtimeSession
 
 from .realtime_model import RealtimeModel
@@ -7,4 +9,5 @@
     "GrokVoices",
     "RealtimeModel",
     "RealtimeSession",
+    "TurnDetection",
 ]