While the word 'simply' is usually added to encourage readers, it often has the
opposite effect and may even appear condescending, especially when the reader
runs into trouble trying to apply the suggestions from the documentation. It is
almost always an improvement to simply drop the word from the sentence.
(there are more possible improvements like this, we can apply those in separate
PRs)
The command in example is expected to be run from nixpkgs checkout, but
there's no explanation of this. Let's just use system nixpkgs: most
users will have it just working and those who use git checkouts will
figure it out.