[Bugfix] Fix casing warning

[MatthewBonanni]

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.

Purpose

Fix FromAsCasing warning in docker build

Test Plan

DOCKER_BUILDKIT=1 docker build . --target vllm-openai --tag vllm/vllm-openai --file docker/Dockerfile

Test Result

Previously:
=> WARN: FromAsCasing: 'as' and 'FROM' keywords' casing do not match (line 268) 0.0s

Now, no warning.

(Optional) Documentation Update

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[gemini-code-assist]

Code Review

This pull request correctly fixes a FromAsCasing warning in the docker/Dockerfile by capitalizing the as keyword to AS in the FROM instruction. This change aligns with Dockerfile best practices for instruction casing and successfully resolves the build warning as intended. The change is straightforward and looks good.

[mgoin]

Thanks for the find!