ci/check: switch to self-hosted runner

.github/workflows/check.yml

@@ -7,7 +7,7 @@ on:
 jobs:
   check:
     name: Check that the module is valid
-    runs-on: ubuntu-latest
+    runs-on: self-hosted
     timeout-minutes: 40
     steps:
       - uses: actions/checkout@v4
@@ -15,7 +15,7 @@ jobs:
         with:
           nix_path: nixpkgs=channel:nixos-unstable
           github_access_token: ${{ secrets.GITHUB_TOKEN }}
-      - uses: cachix/cachix-action@v12
+      - uses: cachix/cachix-action@master
         with:
           name: nix-community
           authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'