Is AllowCors necessary to dynamic options loaders?

## Issue Type

Please select the type of issue you are reporting:

- Bug Report

## Description

For dynamic options loaders, we are using this code to avoid CORS.

```ts
Object.entries(allowCorsFor(req)).map(([name, value]) => {
ctx.response.headers.set(name, value);
});
```

However, requests from the admin panel should not encounter CORS problems.

## Steps to Reproduce (for bugs)

1. Run a store with deco and apps referenced
2. Remove allowCors code from one of dynamic loaders
- `vtex/loaders/options/productIdByTerm.ts`
3. The dynamic options select will not work

## Expected Behavior

Our admin should be able to do request to loaders without this allowCors explicity.