DOC: update the Series.sort_values docstring

[rafarui]

Checklist for the pandas documentation sprint (ignore this if you are doing
an unrelated PR):

• PR title is "DOC: update the docstring"
• The validation script passes: scripts/validate_docstrings.py <your-function-or-method>
• The PEP8 style check passes: git diff upstream/master -u -- "*.py" | flake8 --diff
• The html version looks good: python doc/make.py --single <your-function-or-method>
• It has been proofread on language by another sprint participant

Please include the output of the validation script below between the "```" ticks:

# paste output of "scripts/validate_docstrings.py <your-function-or-method>" here
# between the "```" (remove this comment, but keep the "```")

If the validation script still gives errors, but you think there is a good reason
to deviate in this case (and there are certainly such cases), please state this
explicitly.

Checklist for other PRs (remove this part if you are doing a PR for the pandas documentation sprint):

• closes #xxxx
• tests added / passed
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry

[pep8speaks]

Hello @rafarui! Thanks for submitting the PR.

• In the file pandas/core/series.py, following are the PEP8 issues :

Line 1888:5: E265 block comment should start with '# '
Line 1894:80: E501 line too long (86 > 79 characters)
Line 1905:80: E501 line too long (123 > 79 characters)
Line 1908:80: E501 line too long (86 > 79 characters)
Line 1923:80: E501 line too long (83 > 79 characters)

[rafarui]

We have removed the Apender because it was not generic. It was made for DataFrame.

[TomAugspurger]

@rafarui do you wish to continue working on this? Sorry we didn't have a chance to review it yesterdya, but if you reopen I'll take a look.

[rafarui]

@TomAugspurger
No need, I had opened this pull request by mistake. The "right"one is this one
#20247

Thanks