feat: ability to ignore/exclude outside collaborators from CODEOWNERS removal

Organizations have outside collaborators that have been given permissions to interact with its repositories.

Currently they will get flagged as non-organization members and a PR will be created to remove them from the `CODEOWNERS` file currently.

Unfortunately, the `github3` library we use has not implemented the ability to detect outside collaborators in an organization. There is an [existing issue](https://github.com/sigmavirus24/github3.py/issues/925) on the library.