Remove VLLM_ASCEND_ENABLE_DENSE_OPTIMIZE (#5272)

`VLLM_ASCEND_ENABLE_DENSE_OPTIMIZE` is only used together with
`VLLM_ASCEND_ENABLE_PREFETCH_MLP` which is useless totally. This PR
remove it.
- vLLM version: release/v0.13.0
- vLLM main:
ad32e3e19c

Signed-off-by: wangxiyuan <wangxiyuan1007@gmail.com>

vllm_ascend/utils.py

@@ -772,10 +772,6 @@ def matmul_allreduce_enable() -> bool:
     return envs_ascend.VLLM_ASCEND_ENABLE_MATMUL_ALLREDUCE
 
 
-def dense_optim_enable() -> bool:
-    return envs_ascend.VLLM_ASCEND_ENABLE_DENSE_OPTIMIZE
-
-
 def enable_sp(vllm_config=None, enable_shared_expert_dp: bool = False) -> bool:
     global _ENABLE_SP
     if _ENABLE_SP is None: