fix(engine): loop error on close (#285)

Author: vishwarajanand

src/langchain_google_cloud_sql_pg/engine.py

@@ -416,7 +416,7 @@ def _run_as_sync(self, coro: Awaitable[T]) -> T:
 
  async def close(self) -> None:
  """Dispose of connection pool"""
- await self._pool.dispose()
+ await self._run_as_async(self._pool.dispose())
 
  async def _ainit_vectorstore_table(
  self,