add missing name option to flash test example [ci skip]

guides/source/testing.md

@@ -830,7 +830,7 @@ end
 If we run our test now, we should see a failure:
 
 ```bash
-$ bin/rails test test/controllers/articles_controller_test.rb test_should_create_article
+$ bin/rails test test/controllers/articles_controller_test.rb -n test_should_create_article
 Run options: -n test_should_create_article --seed 32266
 
 # Running:
@@ -868,7 +868,7 @@ end
 Now if we run our tests, we should see it pass:
 
 ```bash
-$ bin/rails test test/controllers/articles_controller_test.rb test_should_create_article
+$ bin/rails test test/controllers/articles_controller_test.rb -n test_should_create_article
 Run options: -n test_should_create_article --seed 18981
 
 # Running: