Fix a build error

This commit fixes the following build error:

```console
Failures:

  1) RuboCop Project Changelog entry contributor name has a unique contributor name
     Failure/Error: expect(contributor_names.uniq.size).to eq contributor_names.size

       expected: 621
            got: 620

       (compared using ==)
     Shared Example Group: "has Changelog format" called from ./spec/project_spec.rb:280
```

https://github.com/rubocop/rubocop/actions/runs/5355047135/jobs/9712842760

CHANGELOG.md

@@ -7171,4 +7171,3 @@
 [@nevans]: https://github.com/nevans
 [@iMacTia]: https://github.com/iMacTia
 [@rwstauner]: https://github.com/rwstauner
-[@rwstauner]: https://github.com/rwstauner