ci: hard-code the flake-closure-diff runner

Author: yocaba

.github/workflows/flake-closure-diff-self.yml

@@ -20,6 +20,3 @@ permissions:
 jobs:
   closure-diff:
     uses: ./.github/workflows/flake-closure-diff.yml
-    secrets:
-      cachix-auth-token: ${{ secrets.CACHIX_AUTH_TOKEN }}
-      cachix-signing-key: ${{ secrets.CACHIX_SIGNING_KEY }}

.github/workflows/flake-closure-diff.yml

@@ -21,10 +21,6 @@ on:
           both sides are addressed as <path>#<attribute>.
         type: string
         default: devShells.x86_64-linux.default
-      runs-on:
-        description: Runner for the job.
-        type: string
-        default: ubuntu-24.04
     secrets:
       cachix-auth-token:
         required: false
@@ -37,7 +33,7 @@ permissions:
 jobs:
   closure-diff:
     name: Diff flake closures
-    runs-on: ${{ inputs.runs-on }}
+    runs-on: ubuntu-24.04
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
         with: