docs(overview): Fix event data region in mermaid

[itaybre]

DESCRIBE YOUR PR

Fix the Event Data name to reflect silo region.

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Name	Status	Preview	Comments	Updated (UTC)
develop-docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	May 8, 2025 7:36pm

2 Skipped Deployments

Name	Status	Preview	Comments	Updated (UTC)
changelog	⬜️ Ignored (Inspect)			May 8, 2025 7:36pm
sentry-docs	⬜️ Ignored (Inspect)			May 8, 2025 7:36pm