nbstripout for removing jupyter notebook outputs

[RichardP-tt]

In place of

qa-of-code-guidance/book/version_control.md

Line 511 in 611df2c

This approach has been borrowed from this [blog post by Yury Zhauniarovich](https://zhauniarovich.com/post/2020/2020-10-clearing-jupyter-output-p3/).

and the explanation above it, is it worth considering the older and possibly more well-established approach of nbstripout ?