Run Isort on tests/indexes part three
- [x] partial #23334
- [x] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
Run `isort -rc pandas/tests/indexes/`

PR is capped at 20 files. So this is not all the files modified from `pandas/tests/indexes/`. So this is Part Three of this directory `pandas/tests/indexes/`. 
