minor #6644 [Console] Fix wrong quotes in QuestionHelper::setInputStream() (chalasr)

This PR was merged into the 2.7 branch.

Discussion
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[Console] Fix wrong quotes in QuestionHelper::setInputStream()

As pointed by [this Stack Overflow question](http://stackoverflow.com/questions/37709966/symfony-interactive-command-test-ends-with-runtimeexception/37712073), the code example showing how to test a command that interacts with the user is wrong.

The reason is that `\n` between simple quotes are [not considered as break lines](http://stackoverflow.com/questions/2531969/print-newline-in-php-in-single-quotes) in PHP, even escaped with an additional `\`.

Commits
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5679e2d Fix wrong quotes in QuestionHelper::setInputStream()

Author: xabbuh

components/console/helpers/questionhelper.rst

@@ -294,7 +294,7 @@ from the command line, you need to set the helper input stream::
         $commandTester = new CommandTester($command);
 
         $helper = $command->getHelper('question');
-        $helper->setInputStream($this->getInputStream('Test\\n'));
+        $helper->setInputStream($this->getInputStream("Test\n"));
         // Equals to a user inputting "Test" and hitting ENTER
         // If you need to enter a confirmation, "yes\n" will work