rails-new: update test

Signed-off-by: Rui Chen <rui@chenrui.dev>

Formula/r/rails-new.rb

@@ -7,15 +7,18 @@ class RailsNew < Formula
   head "https://github.com/rails/rails-new.git", branch: "main"
 
   depends_on "rust" => :build
+  depends_on "docker" => :test
 
   def install
     system "cargo", "install", *std_cargo_args
   end
 
   test do
+    ENV["DOCKER_HOST"] = "unix://#{testpath}/invalid.sock"
+
     assert_match version.to_s, shell_output("#{bin}/rails-new --version")
 
     output = shell_output("#{bin}/rails-new testapp 2>&1", 101)
-    assert_match "failed to fetch metadata", output
+    assert_match "Cannot connect to the Docker daemon", output
   end
 end