[llm][data] Change example pip install to ray[llm]

[eicherseiji]

Description

• Markdown instructions out of date with notebook contents
• Notebooks are already tested in CI, but with ray-llm image
• ray[llm] already bundles data, and is used for ray-llm image, so it more accurately reflects the tested configuration

Additional information

Manual tests complete successfully with rayproject/ray-llm:2.50.1-py311-cu128:

[gemini-code-assist]

Code Review

This pull request updates the installation instructions in two example notebooks to use ray[llm], which is a good step for consistency. The change for vllm-with-lora.ipynb looks correct. However, for vllm-with-structural-output.ipynb, the xgrammar dependency was removed. Since ray[llm] does not appear to install xgrammar, this could break the notebook for users. I've added a comment with a suggestion to re-introduce xgrammar to the installation command for that specific notebook.