Remove ms.product metadata from index.md

[gewarren]

I assume this was supposed to be ms.prod originally. But should be covered by ms.service in the docfx.json file anyway.

[learn-build-service-prod]

PoliCheck Scan Report

The following report lists PoliCheck issues in PR files. Before you merge the PR, you must fix all severity-1 and severity-2 issues. The AI Review Details column lists suggestions for either removing or replacing the terms. If you find a false positive result, mention it in a PR comment and include this text: #policheck-false-positive. This feedback helps reduce false positives in future scans.

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[learn-build-service-prod]

Learn Build status updates of commit 9b0960f:

✅ Validation status: passed

File	Status	Preview URL	Details
reference/module/index.md	✅Succeeded	View

For more details, please refer to the build report.