[13.2 Regression] Project list API doesn't work as expected anymore for the owned attribute

Summary

The owned attribute in the project returns now more projects than it should

Steps to reproduce

Explaination by @eric.frederich from the python-gitlab functional tests: https://github.com/python-gitlab/python-gitlab/issues/1148#issuecomment-670725001

Documentation for listing project says owned will Limit by projects explicitly owned by the current user.
Relavent lines in python_test_v4.py are:

group2 = gl.groups.create({"name": "group2", "path": "group2"})
add another owner otherwise we cannot delete ourselves
user2 = gl.users.create({"email": "user2@test.com", "username": "user2", "name": "user2", "password": "user2_pass"})
group2.members.create({"access_level": gitlab.const.OWNER_ACCESS, "user_id": user2.id})
group2.members.delete(gl.user.id)
gr2_project = gl.projects.create({"name": "gr2_project", "namespace_id": group2.id})
On 13.1.4-ce.0 this project does not get returned under gl.projects.list(owned=True)
Under 13.2.0-ce.0 it does.

@eric.frederich Please feel free to add some comments here to explain this in more detail.