mod: adjusted workflow file

.gitea/workflows/publish-attic.yaml

@@ -3,26 +3,23 @@ name: Publish packages to Attic
 on:
   push:
     branches:
-      - main
+      - master
   workflow_dispatch:
 
 jobs:
   publish:
-    runs-on: ubuntu-latest
+    runs-on: docker.io/nixos/nix
 
     env:
       ATTIC_SERVER: ${{ secrets.ATTIC_SERVER }}
       ATTIC_CACHE: ${{ secrets.ATTIC_CACHE }}
       ATTIC_TOKEN: ${{ secrets.ATTIC_TOKEN }}
+      NIX_CONFIG: experimental-features = nix-command flakes
 
     steps:
       - name: Check out repository
         uses: actions/checkout@v4
 
-      - name: Install Nix
-        uses: DeterminateSystems/nix-installer-action@v18
-        continue-on-error: true
-
       - name: Install Attic client
         shell: bash
         run: |