version 1.16.0 new feature "Export COCO with images" are giving wrong file_name

**Describe the bug**
I think the new export option "Export COCO with images" in the version 1.16.0 is to replace the old "Export COCO"
But the image path exported was different with the older version.

version 1.16.0:
"file_name": "..\\..\\label-studio\\label-studio\\media\\upload\\4\\cb0618f6-BitBlt_True_3840x2160_1742563473858.5857_original.png"

older version:
"file_name": "images\\cb0618f6-BitBlt_True_3840x2160_1742563473858.5857_original.png"

that make the data unusable, it should be relative to the result.json, like older version

**Environment (please complete the following information):**
- OS: [Windows 11]
- Label Studio Version [1.16.0]