MAINT: Clarify supported Stata dta versions
Test against old Stata versions and remove text indicating support
for versions which do not work reliably

closes #26667

- [x] closes #26667
- [X] tests added / passed
- [X] passes `black pandas`
- [X] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry
