ci: fetch latest installer from hydra

.github/workflows/test.yml

@@ -115,14 +115,22 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
     - uses: actions/checkout@v4
-    - name: Install Nix
-      uses: cachix/install-nix-action@V27
+
+    - id: latest_installer
+      name: Fetch latest installer from Hydra
+      run: |
+        install_url=$(curl --header 'Accept: application/json' --location \
+          https://hydra.nixos.org/job/nix/master/installerScript/latest-finished \
+          | jq -r '.buildproducts."1".path')
+        echo "install_url=$install_url" >> $GITHUB_OUTPUT
+
+    - uses: cachix/install-nix-action@V27
       with:
-        nix_path: nixpkgs=channel:nixos-22.11
-        install_url: https://nixos-nix-install-tests.cachix.org/serve/kkq45x7yrzvxq8627fi6hkswnfa7mg2l/install
-        install_options: '--tarball-url-prefix https://nixos-nix-install-tests.cachix.org/serve'
+        install_url: ${steps.latest_installer.outputs.install_url}
+
     - run: yarn install --frozen-lockfile
     - run: yarn build
+
     - name: Test public cache
       uses: ./
       with: