DOC: Freeze old whatsnew notes?
Currently on master, we have a new failure from the `0.10.0.txt` whatsnew due to the `line_width` option being removed.

Rather than continuing to fix these old examples due to backwards comparability breaks in pandas, could we convert the old `..ipython:: python` blocks to regular `.. code-block:: python` examples so they aren't run anymore? Ideally we could write a script that runs them one last time, captures the output, and updates the `.rst`. Anyone have interest in seeing if that's possible?