Update Dockerfile.rocm

[JeniferC99]

Purpose

https://ontrack-internal.amd.com/browse/SWDEV-564802

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.

[github-actions]

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[gshtras]

Having put aside the potential conflict when using the proper base image with FA installed
You can't just inflate the build step by hours. FA needs to be installed on the base image before you start vLLM docker build.