chore(cloudfront-origins): remove the unused variable from the unit test (#35753)

### Issue # (if applicable)

None

### Reason for this change

There is the unused `otherStack` variable in `functio-url-origin.test.ts`.

```
let otherStack: Stack;

beforeEach(() => {
  otherStack = new Stack():
});
```

### Description of changes

Remove `otherStack` definition

### Describe any new or updated permissions being added

None


### Description of how you validated changes

Existing unit test

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: badmintoncryer

packages/aws-cdk-lib/aws-cloudfront-origins/test/function-url-origin.test.ts

@@ -6,11 +6,9 @@ import { Duration, Stack } from '../../core';
 import { FunctionUrlOrigin } from '../lib';
 
 let stack: Stack;
-let otherStack: Stack;
 
 beforeEach(() => {
   stack = new Stack();
-  otherStack = new Stack();
 });
 
 test('Correctly renders the origin for a Lambda Function URL', () => {