Fix missing colon

Author: chalasr

components/console/helpers/questionhelper.rst

@@ -277,7 +277,7 @@ Testing a Command that Expects Input
 ------------------------------------
 
 If you want to write a unit test for a command which expects user inputs
-from the command line, you need to set the inputs like this:
+from the command line, you need to set the inputs like this::
 
     use Symfony\Component\Console\Tester\CommandTester;