Delete CODEOWNERS (cosmos#971)

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## Overview

As discussed in the retro, we are removing the CODEOWNERs file so that
it doesn't conflict with the auto-review-request github action. I have
also disabled the branch project rule for requiring codeowner approval.

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## Checklist

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- [x] New and updated code has appropriate documentation
- [x] New and updated code has new and/or updated testing
- [x] Required CI checks are passing
- [x] Visual proof for any user facing features like CLI or
documentation updates
- [x] Linked issues closed with keywords