build(nix): Update nixpkgs from 23.11 to 24.05

Update to newer nixpkgs version to get clang-format 19, matching
the local development environment (clang-format 19.1.7).

This ensures consistent formatting between local pre-commit hooks
and CI checks, avoiding format check failures due to version
differences in clang-format behavior.

Author: ahojukka5

flake.nix

@@ -6,7 +6,7 @@
 
   # Inputs define external dependencies for this flake.
   inputs.nixpkgs.url =
-    "github:NixOS/nixpkgs/nixos-23.11"; # Nixpkgs repository for system packages.
+    "github:NixOS/nixpkgs/nixos-24.05"; # Nixpkgs repository for system packages.
   inputs.flake-utils.url =
     "github:numtide/flake-utils"; # Utility library for flakes.