Run ruff format on a few files.

[huachenheli]

Summary:
Related to #23449

Test Plan:

(vllm) [huachenheli@devgpu039.dkl2 ~/github/vllm (lint)]$ ruff format tests/entrypoints/test_chat_utils.py
1 file reformatted
(vllm) [huachenheli@devgpu039.dkl2 ~/github/vllm (lint)]$ ruff format vllm/entrypoints/chat_utils.py
1 file reformatted
(vllm) [huachenheli@devgpu039.dkl2 ~/github/vllm (lint)]$ ruff format vllm/entrypoints/openai/serving_engine.py
1 file reformatted

Reviewers:
@DarkLight1337

Subscribers:

Tasks:

Tags:

Purpose

Test Plan

Test Result

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Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.
• (Optional) Release notes update. If your change is user facing, please update the release notes draft in the Google Doc.

[gemini-code-assist]

Code Review

This pull request applies automated code formatting using ruff format across three Python files. The changes are purely stylistic, improving code readability and consistency by adjusting import statements, line wrapping, and quote styles. I have reviewed the changes and found no functional modifications or issues of high or critical severity. The formatting is consistent and aligns with standard Python style guides.