Invalid link to statistics endpoint in endpoints.md

**Please describe your request**
Invalid link to statistics endpoint in `endpoints.md`. I'm not sure if it should be linking to one of these, or something else:

- [statistics-reports.md](https://github.com/DSpace/RestContract/blob/main/statistics-reports.md)
- [statistics-viewevents.md](https://github.com/DSpace/RestContract/blob/main/statistics-viewevents.md)