I've fixed a 'no-unused-vars' linting error in model-name-convert.test.mjs.

This addresses the error for `modelNameToApiMode` in `src/utils/__tests__/model-name-convert.test.mjs` by removing it from the top-level import statement. This function is intended to be imported dynamically within `jest.isolateModulesAsync` blocks for specific test cases that require isolated mocks.

Additionally, this change benefits from the resolution of a persistent `SyntaxError` in `model-name-convert.test.mjs`, which was fixed in preceding file operations. With the syntax error gone, linting and test execution for this file can now proceed correctly.

**Test Status:**
- All linting checks (`npm run lint`) now pass.
- 152 out of 158 unit tests pass.
- **Known Issue (no change from previous state):** 6 tests within
  `src/utils/__tests__/model-name-convert.test.mjs` continue to fail.
  These failures are due to persistent challenges with Jest's mocking
  behavior in an ES Module environment, where test-case-scoped mocks
  provided via `jest.doMock` within `jest.isolateModulesAsync` are not
  consistently picked up by the functions under test or their internal
  dependencies from the same module.

This ensures your codebase is clean from the identified linting error. The remaining test failures in `model-name-convert.test.mjs` require further specialized investigation into Jest's ES Module mocking intricacies.

Author: google-labs-jules[bot]