Docs: Add Google Analytics ID to sphinx configuration

[RobMulla]

Description

This PR enables Google Analytics tracking for the MaxText documentation site.

It adds the google_analytics_id (G-RC6NRK4GNN) to the html_theme_options in docs/conf.py. This is the standard configuration method for sphinx_book_theme.

Changes

• Modified docs/conf.py: Added analytics dictionary to html_theme_options.

Verification

• Verified manually that the configuration matches the sphinx_book_theme documentation.
• Local build verification was skipped due to environment restrictions, but the syntax is correct.

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.
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• 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.

[RobMulla]

Per our discussion this should add the google analytics to the docs. @jacoguzo - Let me know if you can review!

[richjames0]

LGTM

[RobMulla]

Thanks for the reviews! Can this be merged? I believe the CI failures are unrelated and due to the tests themselves not having enough resources.