Remove unused code in fused_moe.py (vllm-project#2805)

### What this PR does / why we need it?
line 408 already declared mc2_mask ,  remove duplicated unused code

### Does this PR introduce _any_ user-facing change?
no

### How was this patch tested?
CI passed with existing test.

- vLLM version: v0.10.1.1
- vLLM main:
vllm-project/vllm@60f0843

Signed-off-by: machenglong <machenglong_yewu@cmss.chinamobile.com>
Signed-off-by: offline0806 <z00858301@china.huawei.com>

Author: machenglong2025

vllm_ascend/ops/fused_moe.py

@@ -425,8 +425,6 @@ def forward(self,
             # When all_reduce_merge is in progress, shared_experts does not do all_reduce in mlp, but waits until shared_experts+router_experts are completed before doing all_reduce
             shared_hidden_states = shared_experts(hidden_states)
 
-        mc2_mask = forward_context.mc2_mask
-
         enable_sp = _metadata_for_padding is not None and _metadata_for_padding.not_dummy_and_is_prefill
         tp_size = get_tensor_model_parallel_world_size()
         if enable_sp: