Update codeowners parsing logic

[rvanasa]

Updates get_team_name() to account for edge cases such as no leading * or more than two listed teams.

[cgundy]

Closing because the * @team-name syntax is indeed correct. See github docs: https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-code-owners#example-of-a-codeowners-file