Fix missing newline at end of file.test.ts

Add newline at the end of the file to comply with style guidelines.

frontend/src/__tests__/utils/file.test.ts

@@ -40,4 +40,4 @@ describe('formatFileSize', () => {
     expect(formatFileSize(1048575)).toBe('1024.0 KB');
     expect(formatFileSize(1048576)).toBe('1.0 MB');
   });
-});
+});