Cleanup Style Issues

```
$ bundle exec rake rubocop
Running RuboCop...
 39/39 files |============ 100 ===========>| Time: 00:00:01 

39 files inspected, no offenses detected
```
We like trailing commas! https://github.com/fastly/Northstar/blob/572ace809529381d9bfe349ae639b9d976908ab4/.rubocop.yml#L338