[flags-sdk] Update demo link on growthbook example (#1145)

### Description

Fixes the demo link

### Demo URL

<!--
Provide a URL to a live deployment where we can test your PR. If a demo
isn't possible feel free to omit this section.
-->

### Type of Change

- [ ] New Example
- [ ] Example updates (Bug fixes, new features, etc.)
- [ ] Other (changes to the codebase, but not to examples)

### New Example Checklist

- [ ] 🛫 `npm run new-example` was used to create the example
- [ ] 📚 The template wasn't used but I carefuly read the [Adding a new
example](https://github.com/vercel/examples#adding-a-new-example) steps
and implemented them in the example
- [ ] 📱 Is it responsive? Are mobile and tablets considered?

Author: chriswdmr

flags-sdk/growthbook/README.md

@@ -4,7 +4,7 @@ This example uses GrowthBook for feature flags with the [Flags SDK](https://flag
 
 ## Demo
 
-[https://flags-sdk-growthbook.vercel.app/](https://flags-sdk-growthbook.vercel.app/)
+[https://growthbook-flags-sdk-example.vercel.app](https://growthbook-flags-sdk-example.vercel.app)
 
 ## How it works