[Docs] Fix async code in serving notebook

[crypdick]

Why are these changes needed?

Async code works in scripts/CI but not on jupyter notebooks on Workspaces.

Related issue number

N/A

Checks

• I've signed off every commit(by using the -s flag, i.e., git commit -s) in this PR.
• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://docs.ray.io/en/master/.
  • I've added any new APIs to the API Reference. For example, if I added a
    method in Tune, I've added it in doc/source/tune/api/ under the
    corresponding .rst file.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

[Copilot]

Pull Request Overview

This PR updates async execution in Jupyter notebooks by adding a wait flag for notebook conversion and converting the serving test into proper async functions with error handling.

• Added --wait flag to ensure the notebook conversion completes before execution.
• Changed test_serve to an async def, added response.raise_for_status(), and updated invocation to use await.
• Adjusted fetch_all_concurrently usage to return predictions and print a completion message.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
doc/source/ray-overview/examples/e2e-xgboost/notebooks/01-Distributed_Training.ipynb	Added --wait flag to the Ray CLI invocation for notebook scripts
doc/source/ray-overview/examples/e2e-timeseries/e2e_timeseries/03-Serving.ipynb	Updated serving test to async, improved HTTP error handling, and updated invocation

Comments suppressed due to low confidence (2)

doc/source/ray-overview/examples/e2e-timeseries/e2e_timeseries/03-Serving.ipynb:302

• [nitpick] Since return_exceptions=True prevents errors from propagating, consider setting it to False or explicitly handling exceptions in the returned responses list to avoid silent failures.

responses = await asyncio.gather(*tasks, return_exceptions=True)

doc/source/ray-overview/examples/e2e-xgboost/notebooks/01-Distributed_Training.ipynb:890

• [nitpick] Consider adding a comment explaining why the --wait flag is necessary for notebook conversions to complete before execution, improving clarity for readers.

--wait \\

[angelinalg]

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