DOC: Replace pandas on Ray in ecosystem.rst with Modin
* Resolves #37247

Signed-off-by: Devin Petersohn <devin.petersohn@gmail.com>

- [x] closes #37247
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry
