Link in "Living with Entropy" callout has vanished

[zkamvar]

It's a bit odd, but the link in https://carpentries.github.io/sandpaper-docs/pull-request.html#callout1 has simply vanished, thus we need a new example.

As in, the link: MCMaurer/Rewrite-R-ecology-lesson#3 now goes to MCMaurer/Rewrite-R-ecology-lesson#3, which is not what I intended to link to in the first place.

I'm not exactly sure what happened, but it appears that pull requests from that repository have been just... wiped away (for example, here's a merge commit from PR 7, but PR 7 does not exist anymore.

[zkamvar]

Note that the example was showing that figures would change even if nothing significant in the lesson changed