 DOC: Update Series min and max docstring. GH22459 
- [ ] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`

Doesn't pass all the tests, but can figure out where they come from.

> Errors found:
>         Closing quotes should be placed in the line after the last text in the docstring (do not close the quotes in the same line as the text, or leave a blank line between the last text and the quotes)
>         Use only one blank line to separate sections or paragraphs

Also I find the way the axis are defined quite confusing. My initial thought was that if you say `axis='index'` it would take apply your function on a row wise basis. 
