CodeOwners are not listed in the eligible approvers when in a cousin group
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### Summary
<!-- Summarize the bug encountered concisely. -->
A ultimate customer is encountering a buggy behavior after implementing CODEOWNERS. The behavior is as described in https://gitlab.com/gitlab-org/gitlab/-/issues/14060#note_363255886.
([internal link](https://gitlab.zendesk.com/agent/tickets/201282))
### Steps to reproduce
<!-- Describe how one can reproduce the issue - this is very important. Please use an ordered list. -->
1. Create a parent group
1. Create 2 subgroups; A & B.
1. In subgroup A, make sure you add all the users that would be acting as codeowners.
1. Under subgroup B, create a project in which you create:
- A CODEWONERS file under `.gitlab` folder, and assign `subgroup A` as codeowners.
- A merge request.
1. Review the MR eligible approvers
### Example Project
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behavior, and link to it here in the bug report. If you are using an older version of GitLab, this
will also determine whether the bug is fixed in a more recent version. -->
### What is the current *bug* behaviour?
<!-- Describe what actually happens. -->
- To have codeowners as eligible approvers for a MR in a certain project, you need to invite `subgroup B` into `subgroup A` or invite `subgroup A` into the project.
- Codeowners widget hides eligible approvers.
### What is the expected *correct* behaviour?
<!-- Describe what you should see instead. -->
- Codeowners appear as eligible approvers without inviting any groups into the the project.
- Codeowners widget appear under eligible approvers.
### Relevant logs and/or screenshots
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as it's tough to read otherwise. -->
### Output of checks
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This bug happens on GitLab.com
#### Results of GitLab environment info
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<details>
<summary>Expand for output related to GitLab environment info</summary>
<pre>
(For installations with omnibus-gitlab package run and paste the output of:
`sudo gitlab-rake gitlab:env:info`)
(For installations from source run and paste the output of:
`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`)
</pre>
</details>
#### Results of GitLab application Check
<!-- Input any relevant GitLab application check information if needed. -->
<details>
<summary>Expand for output related to the GitLab application check</summary>
<pre>
(For installations with omnibus-gitlab package run and paste the output of:
`sudo gitlab-rake gitlab:check SANITIZE=true`)
(For installations from source run and paste the output of:
`sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true`)
(we will only investigate if the tests are passing)
</pre>
</details>
### Possible fixes
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issue