chore: remove codeowners file (backport #8631)

[mergify]

Description

To get a cleaner PR review setup, and because the whole team is code-owners anyway, we are removing the CODEOWNERS file.

---

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Linked to GitHub issue with discussion and accepted design, OR link to spec that describes this work.
• Include changelog entry when appropriate (e.g. chores should be omitted from changelog).
• Wrote unit and integration tests if relevant.
• Updated documentation (docs/) if anything is changed.
• Added godoc comments if relevant.
• Self-reviewed Files changed in the GitHub PR explorer.
• Provide a conventional commit message to follow the repository standards.

---

This is an automatic backport of pull request #8631 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of da5d3d7 has failed:

On branch mergify/bp/release/v8.8.x/pr-8631
Your branch is up to date with 'origin/release/v8.8.x'.

You are currently cherry-picking commit da5d3d7f.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by them: .github/CODEOWNERS

no changes added to commit (use "git add" and/or "git commit -a")

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally