### What this PR does / why we need it?
Currently, the usage of structured output feature in vllm-ascend is
totally the same as that in vllm.
Thus, IMO, it's better to remove this doc directly to avoid some case
that there are some changes in the upstream doc and we don't update our
doc in time, which can be misleading to users.
- vLLM version: v0.12.0
- vLLM main:
ad32e3e19c
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Signed-off-by: shen-shanshan <467638484@qq.com>
551069e53a