Add test for bundle help greet command

Co-authored-by: hsbt <12301+hsbt@users.noreply.github.com>

Author: Copilot

bundler/spec/plugins/command_spec.rb

@@ -82,6 +82,9 @@ def exec(command, args)
 
     bundle "greet -h"
     expect(out).to eq("Usage: bundle greet [NAME]")
+
+    bundle "help greet"
+    expect(out).to eq("Usage: bundle greet [NAME]")
   end
 
   it "raises error on redeclaration of command" do