nix: Update to NixOS 25.05

On-behalf-of: SAP markus.partheymueller@sap.com

Author: parthy

flake.lock

@@ -2,7 +2,7 @@
   description = "OpenStack Packages and Modules for NixOS";
 
   inputs = {
-    nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-24.11";
+    nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-25.05";
     pre-commit-hooks-nix = {
       url = "github:cachix/pre-commit-hooks.nix";
       inputs.nixpkgs.follows = "nixpkgs";