Remove unused globals configuration from Jest config

### Describe the improvement
The Jest configuration currently defines an empty `globals: {}` object.

Since this object is empty, it has no effect on test behavior. Additionally, when using `@swc/jest`, the `globals` field is not required.

Removing unused configuration improves clarity and avoids confusion as Jest continues to deprecate and simplify configuration options.

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### Location
- `frontend/jest.config.ts`

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### Why this matters
- Removes dead configuration with no functional impact
- Improves readability and maintainability of test config
- Avoids confusion around deprecated or unused Jest options
- No change in test behavior intended

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### Suggested change
- Remove the empty `globals: {}` entry from `jest.config.ts`

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### Are you going to work on fixing this?
- [x] Yes
- [ ] No