Update cachix/install-nix-action to version 31 (#572)

* Update cachix/install-nix-action to version 31

* nix: update sources & lock (#580)

---------

Co-authored-by: Paul Baksic <30337881+bakpaul@users.noreply.github.com>
Co-authored-by: Guilhem Saurel <guilhem.saurel@laas.fr>

Author: 3 people

.github/workflows/nix.yml

@@ -11,7 +11,7 @@ jobs:
         os: [ubuntu, macos]
     steps:
       - uses: actions/checkout@v4
-      - uses: cachix/install-nix-action@v27
+      - uses: cachix/install-nix-action@v31
       #- uses: cachix/cachix-action@v15
         #with:
           #name: sofa

flake.lock

@@ -3,11 +3,9 @@
 
   inputs = {
     flake-parts.url = "github:hercules-ci/flake-parts";
-    #nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
-    # ref. https://github.com/NixOS/nixpkgs/pull/348549
-    nixpkgs.url = "github:nim65s/nixpkgs/qt6-libqglviewer";
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
     sofa = {
-      url = "github:nim65s/sofa"; # update this after PR
+      url = "github:sofa-framework/sofa";
       inputs = {
         flake-parts.follows = "flake-parts";
         nixpkgs.follows = "nixpkgs";