Fix test_loaded_gem_types faling in test-bundled-gems (take 2)

`#{gem_dir}/sig` dir does not exist when running `make test-bundled-gems`.
We need to omit the test.

test/repl_type_completor/test_repl_type_completor.rb

@@ -254,9 +254,13 @@ def test_doc_namespace_error
     end
 
     def test_loaded_gem_types
-      result = ReplTypeCompletor.analyze 'RBS::CLI::LibraryOptions.new.loader.', binding: binding
+      # sig directory does not exist when running with test-bundled-gems
+      omit unless Dir.exist?("#{Gem.loaded_specs['prism'].gem_dir}/sig")
+
+      result = ReplTypeCompletor.analyze 'Prism.parse("code").', binding: binding
       candidtes = result.completion_candidates
-      assert_includes candidtes, 'add'
+      assert_includes candidtes, 'success?'
+      assert_includes candidtes, 'failure?'
     end
 
     def test_info