ci: use host runner

.gitea/workflows/build-latex.yaml

@@ -5,7 +5,7 @@ on:
   workflow_dispatch:
 jobs:
   build-latex:
-    runs-on: debian-latest
+    runs-on: nixos
     strategy:
       matrix:
         assignment: [
@@ -14,8 +14,6 @@ jobs:
         ]
     steps:
     - uses: actions/checkout@v3
-    - uses: DeterminateSystems/nix-installer-action@main
-    - uses: DeterminateSystems/magic-nix-cache-action@main
     - run: "nix build .#\"${{ matrix.assignment }}\""
     - uses: actions/upload-artifact@v3
       with: