The CDK example with alpha version is broken

**Describe the content issue**:
The example with alpha version of a library is broken. The way to create an identity pool has changed.

```typescript
const identityPool = new cognito_identitypool.IdentityPool(stack, 'MyNewIdentityPool', {
allowUnauthenticatedIdentities: true,
authenticationProviders: { userPools: [new cognito_identitypool.UserPoolAuthenticationProvider({
userPool: ,
userPoolClient: ,
})] },
});

```

I would use an example with a stable library instead.

**URL page where content issue is**:
https://docs.amplify.aws/react/build-a-backend/graphqlapi/customize-authorization-rules/#public-data-access