remove incompatible steps from self hosted runner

.github/workflows/cachix-deploy.yaml

@@ -9,6 +9,7 @@ on:
         description: "The target to deploy to"
         required: true
         default: "bastion"
+        type: choice
         options:
           - bastion
           - voyager
@@ -53,12 +54,6 @@ jobs:
     runs-on: self-hosted
     steps:
       - uses: actions/checkout@v4
-      - name: Check nix flake inputs
-        uses: DeterminateSystems/flake-checker-action@main
-      - name: Install nix
-        uses: DeterminateSystems/nix-installer-action@main
-        with:
-          extra-conf: experimental-features = nix-command flakes repl-flake
       - name: Run the magic nix cache
         uses: DeterminateSystems/magic-nix-cache-action@main
       - uses: cachix/cachix-action@v14