ERR: Raise on duplicates names in read_csv
- [x] xref #6581
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

thanks @mroeschke  @mroeschke should the entry for this in #6581 be moved to #13777?  (also the docstring for `_validate_names` is now inaccurate)  @jbrockmendel Good catch. Looks like I forgot to move it to #13777 after this PR was merged. which version did this make it into? Looks like 0.25.0