Improve document for **kwargs argument of pandas.Series.to_markdown
This is a follow-up PR of #34594 .  
`pandas.Series.to_markdown` has also same argument.

This PR adds example for `pandas.Series.to_markdown` with tabulate option.

Related Issue: #34568 
Also lgtm - @MarcoGorelli any thoughts? Ha sorry meant to write that on the other PR /azp run <samp>
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</samp> Thanks @nuka137 