Except:
- Instances in documentation, because people in older versions
can't switch to nixfmt yet due to it having pointed to nixfmt-classic
before
- In code that runs based on a CI Nixpkgs version, which is also a bit
older still
- In update script shebangs, because many of them don't pin Nixpkgs, and run
with whatever is in NIX_PATH (and it's not easy to fix this, see
https://github.com/NixOS/nixpkgs/issues/425551)
