TST: boolean indexing using .iloc #20627
- [x] closes #20627
- [1] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`

A simple test was added to close this issue.

/azp run <samp>
Azure Pipelines successfully started running 1 pipeline(s).<br>

</samp> I think everything is done. The last PR is green. Thanks @OlivierLuG 