try to unset vars

.gitea/workflows/check-flake.yaml

@@ -11,16 +11,13 @@ defaults:
 
 jobs:
   check-flake:
-    runs-on: NixOS
+    runs-on: ubuntu-latest
     steps:
-      # - name: Install basic dependencies
-      #   run: apt-get update && apt-get install -y --no-install-recommends sudo curl ca-certificates xz-utils
+      - name: Install basic dependencies
+        run: apt-get update && apt-get install -y --no-install-recommends sudo curl ca-certificates xz-utils
 
-      # - name: Install Nix
-      #   uses: https://github.com/cachix/install-nix-action@v20
-
-      - name: Install dependencies
-        run: nix-shell -p nodejs-18_x
+      - name: Install Nix
+        uses: https://github.com/cachix/install-nix-action@v20
 
       - name: Checkout the repository
         uses: actions/checkout@v3