DOC fix truncated documentation for Series.unstack(), Series. 
fixes https://github.com/pandas-dev/pandas/issues/31235

Changed "e.g. " to "e.g., "
Changed "a.k.a. " to "also known as"
This helps avoid the truncation caused in the docstring
No strong objection but I do think this is a little hacky. Do you know where this limitation is being imposed? The issue here is that, every time a ". " (full stop + space) is encountered, it's presumed to be the end of a one line docstring function description. Thanks @anjalis2112 