README: Remove the pills (#4181)

This removes the Nix Pills reference, because they are not a good
introduction to the Nix ecosystem, but rather a thorough explanation
of many disparate things. Reading through them might give some light
bulb moments for an intermediate reader, but that does not mean that
they're good for a beginner.

I've also removed the mention of infinite recursion without source
location. That's an old meme for a problem that has been mostly
solved. Mentioning it here has two effects:

- Propagate the outdated meme.

- Make users insensitive to bad errors. Learned helplessness. That
  kind of thing. What we really want is for them to report bad error
  messages, so that they can be fixed. And they can be fixed; just
  report them at `NixOS/nix`.

README.md

@@ -36,11 +36,9 @@ Words of warning
 ----------------
 
 Unfortunately, it is quite possible to get difficult to understand
-errors when working with Home Manager, such as infinite loops with no
-clear source reference. You should therefore be comfortable using the
-Nix language and the various tools in the Nix ecosystem. Reading
-through the [Nix Pills][] document is a good way to familiarize
-yourself with them.
+errors when working with Home Manager. You should therefore be
+comfortable using the Nix language and the various tools in the Nix
+ecosystem.
 
 If you are not very familiar with Nix but still want to use Home
 Manager then you are strongly encouraged to start with a small and
@@ -125,7 +123,6 @@ This project is licensed under the terms of the [MIT license](LICENSE).
 [configuration options]: https://nix-community.github.io/home-manager/options.html
 [#home-manager]: https://webchat.oftc.net/?channels=home-manager
 [OFTC]: https://oftc.net/
-[Nix Pills]: https://nixos.org/guides/nix-pills/
 [Nix Flakes]: https://nixos.wiki/wiki/Flakes
 [nix-darwin]: https://github.com/LnL7/nix-darwin
 [manual standalone install]: https://nix-community.github.io/home-manager/index.html#sec-install-standalone