test: remove Jest references from skipped gh-desktop-release-notification tests

The tests were already skipped with describe.skip but still contained
Jest API calls (jest.fn(), jest.mock(), etc.) which caused errors when
the file was parsed by Bun's test runner.

Simplified the file to only contain the empty describe.skip block until
these tests can be properly converted to use Bun's mocking API.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: snomiao