pspg: 2.0.4 -> 2.1.8 (#71758)
pspg: 2.0.4 -> 2.1.8 (#71758)

* pspg: 2.0.4 -> 2.1.8

Semi-automatic update generated by
https://github.com/ryantm/nixpkgs-update tools. This update was made
based on information from
https://repology.org/metapackage/pspg/versions

* pspg: cleanup

pkgconfig is now found automatically

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs