Remove duplicate fields from project spaces response

[risonsimon]

Describe the bug
A clear and concise description of what the bug is.

Project spaces response json has duplicate fields. These duplicate fields are child fields of a parent field in a space.

To Reproduce
Steps to reproduce the behavior:

1. Send api request to /projects/<slug>/spaces.
2. Insides the fields array, there are duplicate fields

Expected behavior
The child fields should not be duplicated

Screenshots
Here fields with id 4 and 5 are duplicated.