test/nixos-search: fix wrong flake being tested

Now the test targets the main nix-bitcoin flake instead of the
nixos-search flake.

Also remove `NIX_PATH`, which is no longer required.

test/nixos-search/ci-test.sh

@@ -17,7 +17,5 @@ if [[ ${CACHIX_SIGNING_KEY:-} ]]; then
     cachix push $cachixCache $(type -P flake-info);
 fi
 
-# flake-info requires '<nixpkgs>'
-export NIX_PATH=nixpkgs=$(nix eval --raw .#nixpkgsPath)
 echo "Running flake-info (nixos-search)"
-flake-info flake ./.
+flake-info flake ../..