[V0 deprecation] Deprecate V0 Neuron backend (#21159)

Signed-off-by: Woosuk Kwon <woosuk.kwon@berkeley.edu>

vllm/distributed/device_communicators/neuron_communicator.py

@@ -1,20 +0,0 @@
-# SPDX-License-Identifier: Apache-2.0
-# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
-import torch
-
-from vllm.distributed.device_communicators.base_device_communicator import (
-    DeviceCommunicatorBase)
-from vllm.platforms import current_platform
-
-if current_platform.is_neuron():
-    import torch_xla.core.xla_model as xm
-
-
-class NeuronCommunicator(DeviceCommunicatorBase):
-
-    def all_reduce(self, x: torch.Tensor) -> torch.Tensor:
-        return xm.all_reduce(xm.REDUCE_SUM, x)
-
-    def all_gather(self, x: torch.Tensor, dim: int = -1) -> torch.Tensor:
-        assert dim == -1, "Neuron only supports dim=-1 for all-gather."
-        return xm.all_gather(x, dim=dim)