actions: use proper git clone

Signed-off-by: lucasew <[email protected]>

.github/workflows/nixpkgs-review.yml

@@ -35,12 +35,6 @@ jobs:
       - name: Free up space
         uses: lucasew/action-i-only-care-about-nix@main
         if: ${{ github.event.inputs.free-space }}
-      - name: Get nixpkgs
-        uses: actions/checkout@v2
-        with:
-          repository: NixOS/nixpkgs
-          ref: master
-          path: ./nixpkgs
       - name: Prepare for Nix if cleaned up
         if: ${{ github.event.inputs.free-space }}
         run: |
@@ -60,6 +54,7 @@ jobs:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         run: |
           { while true; do df -h; uptime; sleep 60; done } &
+          git clone https://github.com/NixOS/nixpkgs nixpkgs
           cd nixpkgs
           nix run nixpkgs#nixpkgs-review -- pr ${{ github.event.inputs.pr }} --post-result --no-shell
       - uses: actions/upload-artifact@v4