ci: Update cachix/install-nix-action

Author: null2264

.github/workflows/build.yml

@@ -10,7 +10,7 @@ jobs:
     steps:
     - uses: actions/checkout@v4
 
-    - uses: cachix/install-nix-action@v27
+    - uses: cachix/install-nix-action@v31
       with:
         github_access_token: ${{ secrets.GITHUB_TOKEN }}