Pass --deployment flag directly

This spec is run only in bundler 2 mode, and it's testing the
`--deployment` flag specifically.

bundler/spec/commands/outdated_spec.rb

@@ -537,7 +537,7 @@ def test_group_option(group)
 
   context "after bundle install --deployment", :bundler => "< 3" do
     before do
-      install_gemfile <<-G, forgotten_command_line_options(:deployment => true)
+      install_gemfile <<-G, :deployment => true
         source "#{file_uri_for(gem_repo2)}"
 
         gem "rack"