Document an alternative method for installing uv

[igorts-git]

Description

UXR studies revealed that pip install uv does not always work. This PR documents an alternative way to install uv using curl command.

FIXES: b/497834280

Tests

Ran the curl command in a clean docker environment to confirm that the curl command is able to install uv.

Checklist

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• I have performed a self-review of my code. For an optional AI review, add the gemini-review label.
• I have necessary comments in my code, particularly in hard-to-understand areas.
• I have run end-to-end tests tests and provided workload links above if applicable.
• I have made or will make corresponding changes to the doc if needed, including adding new documentation pages to the relevant Table of Contents (toctree directive) as explained in our documentation.