VTL example using variables that are not defined in the code snippet

**Page**: [`/cli/graphql/examples-and-solutions`](https://docs.amplify.aws/cli/graphql/examples-and-solutions/#17-get-sales-representatives-ranked-by-order-total-and-sales-period)

**Feedback**:

CDK snippet is missing the variables referenced in the VTL snippet

```ts
const apiIdRef = cdk.Fn.Ref(retVal.api[''].GraphQLAPIIdOutput)
const envRef = cdk.Fn.Ref('env')
```