use default CCL_ZE_IPC_EXCHANGE (#28700)

Signed-off-by: Yan Ma <yan.ma@intel.com>

vllm/v1/worker/xpu_worker.py

@@ -159,12 +159,10 @@ class XPUWorker(Worker):
         else:
             raise RuntimeError(f"Not support device type: {self.device_config.device}")
 
-        ENV_CCL_ZE_IPC_EXCHANGE = os.getenv("CCL_ZE_IPC_EXCHANGE", "pidfd")
         ENV_CCL_ATL_TRANSPORT = os.getenv("CCL_ATL_TRANSPORT", "ofi")
         ENV_LOCAL_WORLD_SIZE = os.getenv(
             "LOCAL_WORLD_SIZE", str(self.parallel_config.world_size)
         )
-        os.environ["CCL_ZE_IPC_EXCHANGE"] = ENV_CCL_ZE_IPC_EXCHANGE
         os.environ["CCL_ATL_TRANSPORT"] = ENV_CCL_ATL_TRANSPORT
         os.environ["LOCAL_WORLD_SIZE"] = ENV_LOCAL_WORLD_SIZE
         os.environ["LOCAL_RANK"] = str(self.local_rank)