remove 'attic use' lines in favor of substituter

.forgejo/workflows/cd.yaml

@@ -12,7 +12,6 @@ jobs:
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4
-      - run: attic login fediversity http://attic.fediversity.net:8080 && attic use demo
 
       - name: Set up SSH key for age secrets and SSH
         run: |

.forgejo/workflows/ci.yaml

@@ -19,7 +19,6 @@ jobs:
     runs-on: nix
     steps:
       - uses: actions/checkout@v4
-      - run: attic login fediversity http://attic.fediversity.net:8080 && attic use demo
       - run: nix-shell --run 'nix-unit ./deployment/data-model-test.nix'
 
   check-mastodon:
@@ -32,32 +31,28 @@ jobs:
     runs-on: nix
     steps:
       - uses: actions/checkout@v4
-      - run: attic login fediversity http://attic.fediversity.net:8080 && attic use demo && nix build .#checks.x86_64-linux.test-peertube-service -L
+      - run: nix build .#checks.x86_64-linux.test-peertube-service -L
 
   check-panel:
     runs-on: nix
     steps:
       - uses: actions/checkout@v4
-      - run: attic login fediversity http://attic.fediversity.net:8080 && attic use demo
-      - run: nix-build -A tests.panel
+      - run: nix-build panel -A tests
 
   check-deployment-basic:
     runs-on: nix
     steps:
       - uses: actions/checkout@v4
-      - run: attic login fediversity http://attic.fediversity.net:8080 && attic use demo
       - run: nix build .#checks.x86_64-linux.deployment-basic -L
 
   check-deployment-cli:
     runs-on: nix
     steps:
       - uses: actions/checkout@v4
-      - run: attic login fediversity http://attic.fediversity.net:8080 && attic use demo
       - run: nix build .#checks.x86_64-linux.deployment-cli -L
 
   check-deployment-panel:
     runs-on: nix
     steps:
       - uses: actions/checkout@v4
-      - run: attic login fediversity http://attic.fediversity.net:8080 && attic use demo
       - run: nix build .#checks.x86_64-linux.deployment-panel -L