Tutorial packaging-existing-software needs update

[aquanjsw]

The local code search related content under https://nix.dev/tutorials/packaging-existing-software#search-nixos-org is outdated due to the deleted xorg set.

[ohorsey]

This is what I came here to say, thanks.

This defeats the purpose of the tutorial in a way that's really frustrating/infuriating, an abbreviation of the section in question is

'there are different ways to determine dependencies, let's walk through how the easy way doesn't work here because X11 is ubiquitous, but look at the method that does work!"