flake.lock: Update

Flake lock file updates:

• Updated input 'flake-compat':
    'github:edolstra/flake-compat/35bb57c0c8d8b62bbfd284272c928ceb64ddbde9' (2023-01-17)
  → 'github:edolstra/flake-compat/0f9255e01c2351cc7d116c072cb317785dd33b33' (2023-10-04)
• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/dfcffbd74fd6f0419370d8240e445252a39f4d10' (2023-07-24)
  → 'github:NixOS/nixpkgs/63143ac2c9186be6d9da6035fa22620018c85932' (2024-01-02)
• Updated input 'phps':
    'github:fossar/nix-phps/80d0393d0fcbe40f715d373308afd280fd5a63f3' (2023-07-25)
  → 'github:fossar/nix-phps/d242ccad64fbbd1f44ddc96d6510904922a4e3d1' (2024-01-06)
• Updated input 'phps/flake-compat':
    'github:edolstra/flake-compat/35bb57c0c8d8b62bbfd284272c928ceb64ddbde9' (2023-01-17)
  → 'github:edolstra/flake-compat/0f9255e01c2351cc7d116c072cb317785dd33b33' (2023-10-04)
• Updated input 'phps/nixpkgs':
    'github:NixOS/nixpkgs/dfcffbd74fd6f0419370d8240e445252a39f4d10' (2023-07-24)
  → 'github:NixOS/nixpkgs/63143ac2c9186be6d9da6035fa22620018c85932' (2024-01-02)
• Updated input 'phps/utils':
    'github:numtide/flake-utils/919d646de7be200f3bf08cb76ae1f09402b6f9b4' (2023-07-11)
  → 'github:numtide/flake-utils/4022d587cbbfd70fe950c1e2083a02621806a725' (2023-12-04)
• Updated input 'utils':
    'github:numtide/flake-utils/919d646de7be200f3bf08cb76ae1f09402b6f9b4' (2023-07-11)
  → 'github:numtide/flake-utils/4022d587cbbfd70fe950c1e2083a02621806a725' (2023-12-04)

Removing psalm because it does not build with PHP 7.4 or PHP 8.0 any more.

flake.nix

@@ -64,7 +64,6 @@
               php.packages.composer
 
               # Back-end code validation.
-              php.packages.psalm
               php.packages.phpstan
 
               # npm for front-end.