Remove installer and installer_test GHAs for now

We never got them set up, as evidenced by missing script.

.github/workflows/ci.yml

@@ -56,43 +56,3 @@ jobs:
           _CACHIX_SECRETS: ${{ secrets.CACHIX_SIGNING_KEY }}${{ secrets.CACHIX_AUTH_TOKEN }}
         run: |
           echo "::set-output name=secret::${{ env._CACHIX_SECRETS != '' }}"
-
-  installer:
-    needs: [tests, check_cachix]
-    if: github.event_name == 'push' && needs.check_cachix.outputs.secret == 'true'
-    runs-on: ubuntu-latest
-    outputs:
-      installerURL: ${{ steps.prepare-installer.outputs.installerURL }}
-    steps:
-    - uses: actions/checkout@v4
-      with:
-        fetch-depth: 0
-    - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
-    - uses: cachix/install-nix-action@v30
-      with:
-        install_url: https://releases.nixos.org/nix/nix-2.20.3/install
-    - uses: cachix/cachix-action@v15
-      with:
-        name: '${{ env.CACHIX_NAME }}'
-        signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'
-        authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
-        cachixArgs: '-v'
-    - id: prepare-installer
-      run: scripts/prepare-installer-for-github-actions
-
-  installer_test:
-    needs: [installer, check_cachix]
-    if: github.event_name == 'push' && needs.check_cachix.outputs.secret == 'true'
-    strategy:
-      fail-fast: false
-      matrix:
-        os: [ubuntu-latest, macos-latest]
-    runs-on: ${{ matrix.os }}
-    steps:
-    - uses: actions/checkout@v4
-    - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
-    - uses: cachix/install-nix-action@v30
-      with:
-        install_url: '${{needs.installer.outputs.installerURL}}'
-        install_options: "--tarball-url-prefix https://${{ env.CACHIX_NAME }}.cachix.org/serve"
-    - run: nix-instantiate -E 'builtins.currentTime' --eval