DOC: Explicit how 'cond' is updated on 'where'
This PR updates the section notes on `DataFrame.where(cond, other=nan, *, inplace=False, axis=None, level=None)` docstring.
Currently pandas isn't explicit on who is being updated when  `cond` is misaligned with `other`. Just made that explicit to avoid confusion.
@aureliobarbosa kindly link your PR to the GitHub issue @samukweku  There is no open issue related to this PR. I found the problem and just tried to fix it directly through a PR because recently I did the same on CPython and there the instructions were clear that if it where very small contribution (typo, link, etc) it wasn't necessary to open an issue. 

I just added three words to definite a relation explicitly. Should I open a new issue? Kindly ignore my comments . I'll let @pandas-dev/pandas-core team speak on this. @phofl @Dr-Irv  This pull request is stale because it has been open for thirty days with no activity. Please [update](https://pandas.pydata.org/pandas-docs/stable/development/contributing.html#updating-your-pull-request) and respond to this comment if you're still interested in working on this.