Upgrade GrowthBook to latest version (v1.9.0)

[fajarb]

Use Case

The latest version brings many new and improved features such as following:

• Frequentist Stats Engine
• GrowthBook Proxy Server
• Event Webhooks
• Feature Flag Scheduling
• REST API
• And some more

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Message from the maintainers:

Excited about this feature? Give it a 👍. We factor engagement into prioritization.

[Alden-7C]

I would really like this too C:

[Alex-7C]

Also interested. We use heap and support was added later.