Docs: Sync metadata.md with latest plugin.schema.json

[mckn]

Summary

• Regenerates metadata.md by running npm -w website run prebuild to sync it with the latest upstream plugin.schema.json
• Fixes the "metadata.md is out of sync" CI check that is currently blocking PR Docs: Add datasource picker virtualization migration guide #2581
• The schema change is a minor wording update: "adhoc filters" → "filters" for the multiValueFilterOperators field description

Test plan

• Verify the "Verify metadata.md" CI check passes

🤖 Generated with Claude Code

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[Copilot]

Pull request overview

This PR updates the generated plugin.json metadata reference to match the latest upstream plugin.schema.json, resolving the “metadata.md is out of sync” CI failure.

Changes:

• Regenerates docusaurus/docs/reference/metadata.md to reflect the current schema output.
• Updates the multiValueFilterOperators description wording from “adhoc filters” to “filters”.