ci: remove cachix action

All the extra binary cache lookups and uploads to Cachix make the
build quite a bit slower than necessary.

.github/workflows/test.yml

@@ -15,10 +15,6 @@ jobs:
     - uses: cachix/install-nix-action@v23
       with:
         nix_path: nixpkgs=channel:nixos-unstable
-    - uses: cachix/cachix-action@v13
-      with:
-        name: nix-community
-        authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
     - run: |
         if grep -R --exclude stdlib-extended.nix literalExample modules ; then
           echo "Error: literalExample should be replaced by literalExpression" > /dev/stderr