workflow: remove nixUnstable build

.github/workflows/cachix.yml

@@ -38,25 +38,3 @@ jobs:
           name: lava
           authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
       - run: nix build -L .#linux-lava
-
-  build-nix:
-    runs-on: ubuntu-latest
-    name: Build nixUnstable for aarch64-linux
-    steps:
-      - uses: actions/checkout@v3
-        with:
-          fetch-depth: 0
-      - uses: dbhi/qus/action@main
-        with:
-          targets: arm aarch64
-      - uses: cachix/install-nix-action@v17
-        with:
-          install_url: https://github.com/numtide/nix-unstable-installer/releases/download/nix-2.12.0pre20220930_89ca75c/install
-          extra_nix_config: |
-            extra-platforms = aarch64-linux arm-linux
-            experimental-features = nix-command flakes
-      - uses: cachix/cachix-action@v10
-        with:
-          name: lava
-          authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
-      - run: nix build -L .#packages.aarch64-linux.nixUnstable