[Cleanup][v1]:remote guided-decoding-backend for example

[calvin0327]

Exec the example will result in the following error because, in v1, the Request-level structured output does not support the guided_decoding_backend parameter.

https://github.com/vllm-project/vllm/blob/main/vllm/v1/engine/processor.py#L161

[github-actions]

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[russellb]

thanks!