Suggestions for paper

## 📑 Description This PR adds a few edit suggestions for the `PerMetrics` paper for JOSS, as described [in this issue.](https://github.com/openjournals/joss-reviews/issues/6143#issuecomment-1979978534) ## ✅ Checks <!-- Make sure your pr passes the CI checks and do check the following fields as needed - --> - [x] My pull request adheres to the code style of this project - [x] My code requires changes to the documentation - [ ] I have updated the documentation as required - [x] All the tests have passed