DOC: Added documentation to name and fastpath arguments in series.py


- [X] closes #27178
- [N/A] tests added / passed
- [N/A] passes `black pandas`
- [N/A] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [N/A] whatsnew entry

This is a duplicate of #27960, please help with that PR if you've got something that it's better than what's in there. Thanks!