ci: Don't dogfood installer from master

CI on release branches should be stable, otherwise backporting
might become flaky and unreliable. Dogfooding only really makes
sense for CI on master branch, where failures are not as tedious
to work around.

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
         fetch-depth: 0
     - uses: ./.github/actions/install-nix-action
       with:
-        dogfood: true
+        dogfood: false
         extra_nix_config:
           experimental-features = nix-command flakes
         github_token: ${{ secrets.GITHUB_TOKEN }}
@@ -42,7 +42,7 @@ jobs:
     - uses: ./.github/actions/install-nix-action
       with:
         github_token: ${{ secrets.GITHUB_TOKEN }}
-        dogfood: true
+        dogfood: false
         # The sandbox would otherwise be disabled by default on Darwin
         extra_nix_config: |
           sandbox = true
@@ -184,7 +184,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: ./.github/actions/install-nix-action
         with:
-          dogfood: true
+          dogfood: false
           extra_nix_config:
             experimental-features = nix-command flakes
           github_token: ${{ secrets.GITHUB_TOKEN }}
@@ -215,7 +215,7 @@ jobs:
           path: flake-regressions/tests
       - uses: ./.github/actions/install-nix-action
         with:
-          dogfood: true
+          dogfood: false
           extra_nix_config:
             experimental-features = nix-command flakes
           github_token: ${{ secrets.GITHUB_TOKEN }}