🐛(agents) fix shutdown exception in metadata extractor

Remove a redundant drain operation causing an exception during the
metadata extractor shutdown.

CHANGELOG.md

@@ -8,6 +8,11 @@ and this project adheres to
 
 ## [Unreleased]
 
+
+### Changed
+
+- 🐛(agents) fix bug when closing metadata-collector
+
 ## [1.18.0] - 2026-06-03
 
 ### Added

src/agents/metadata_collector.py

@@ -324,7 +324,6 @@ class MetadataCollector:
     async def _close_session(self, session: AgentSession) -> None:
         """Close and cleanup VAD monitoring session."""
         try:
-            await session.drain()
             await session.aclose()
         except Exception:
             logger.exception("Error closing session")