### 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:
60f0843ef8
Signed-off-by: machenglong <machenglong_yewu@cmss.chinamobile.com>