[long_seq] remove long_seq env (#4660)

### What this PR does / why we need it?
remove env VLLM_ASCEND_ENABLE_CONTEXT_PARALLEL 

- vLLM version: v0.12.0

---------

Signed-off-by: LookAround <lixushi@huawei.com>
Signed-off-by: ZhangMingWei716 <2894054457@qq.com>
Co-authored-by: ZhangMingWei716 <2894054457@qq.com>
Co-authored-by: wangxiyuan <wangxiyuan1007@gmail.com>

vllm_ascend/spec_decode/mtp_proposer.py

@@ -7,6 +7,7 @@ import torch.nn as nn
 import torch.nn.functional as F
 from vllm.config import (CUDAGraphMode, VllmConfig,
                          get_layers_from_vllm_config, set_current_vllm_config)
+from vllm.distributed import get_pcp_group
 from vllm.forward_context import get_forward_context
 from vllm.logger import init_logger
 from vllm.model_executor.layers.attention_layer_base import AttentionLayerBase
@@ -16,6 +17,8 @@ from vllm.model_executor.model_loader.utils import \
 from vllm.model_executor.models.deepseek_v2 import DeepseekV32IndexerCache
 from vllm.model_executor.models.llama_eagle3 import Eagle3LlamaForCausalLM
 from vllm.utils.math_utils import cdiv
+from vllm.utils.platform_utils import is_pin_memory_available
+from vllm.utils.torch_utils import set_default_torch_dtype
 from vllm.v1.attention.backends.utils import (AttentionMetadataBuilder,
                                               CommonAttentionMetadata)
 from vllm.v1.core.sched.output import SchedulerOutput
@@ -32,15 +35,8 @@ from vllm_ascend.compilation.acl_graph import (ACLGraphWrapper,
                                                update_mla_attn_params)
 from vllm_ascend.spec_decode.interface import Proposer, SpecDcodeType
 from vllm_ascend.utils import (ProfileExecuteDuration, lmhead_tp_enable,
-                               prefill_context_parallel_enable,
                                shared_expert_dp_enabled)
 
-if prefill_context_parallel_enable():
-    from vllm.distributed import get_pcp_group
-
-from vllm.utils.platform_utils import is_pin_memory_available
-from vllm.utils.torch_utils import set_default_torch_dtype
-
 logger = init_logger(__name__)
 
 PADDING_SLOT_ID = -1