### What this PR does / why we need it?
Remove unused assertion in `NPUWorker`, as this has been moved to
`Executor` in vLLM:
aabeb2688f/vllm/executor/uniproc_executor.py (L43)
### Does this PR introduce _any_ user-facing change?
N/A
### How was this patch tested?
CI passed with existing test.
Signed-off-by: MengqingCao <cmq0113@163.com>