Fix spec like I shoulda done before landing #5736

spec/lib/rex/exploitation/cmdstager/certutil_spec.rb

@@ -11,15 +11,9 @@ describe Rex::Exploitation::CmdStagerCertutil do
     described_class.new(exe)
   end
 
-  describe '#cmd_concat_operator' do
-    it "returns &" do
-      expect(cmd_stager.cmd_concat_operator).to eq(" & ")
-    end
-  end
-
   describe '#generate' do
     it "returns an array of commands" do
-      result = cmd_stager.generate(opts)
+      result = cmd_stager.generate
 
       expect(result).to be_kind_of(Array)
       expect(result).to_not be_empty