DOC: follow 0.23.1 template for 0.23.2 whatsnew
xref https://github.com/pandas-dev/pandas/pull/21433 (@gfyoung we changed some things since the v0.23.1.txt file was added)
@jorisvandenbossche : Thanks for letting me know!  BTW, is there a place where we have a blank copy of the `whatsnew` template (i.e. so that an old version of it isn't pushed by accident)? I don't think so, if I add it, I typically copy the last (relevant) one and remove the content @jorisvandenbossche : Got it.  Thanks for clarifying!