Test Steps Custom fields doesn't follow the scheme of JSON when being exported

Description
Test Steps Custom fields doesn't follow the scheme of JSON when being exported using the REST API.

Pre-conditions
Create a Test Step custom field of Text field multi-line

How to reproduce

1. Create a test Steps Custom Field(Text Field Multi-line)
2. Add it to the Test
   
3. Execute the Test
4. Export the information of the Test Run using the REST API

Actual result/Attachments
Wrong JSON Structure:

Expected result
Scheme of the Test Step Custom field should be the same as default Test Steps

Version

• Tested with 5.0.2