minor #7483 Use statement for InputOption added to example (soxyl, javiereguiluz)

This PR was merged into the 2.7 branch.

Discussion
----------

Use statement for InputOption added to example

Hi,

while reading in the docs today I was looking for the namespace of the `InputOption` class. Since it was missing on this page I added it.

Sam

Commits
-------

d263735 Minor tweak
e124ee6 Use statement for InputOption added to example

Author: xabbuh

console/input.rst

@@ -118,6 +118,9 @@ simply as a boolean flag without a value (e.g.  ``--yell``).
 For example, add a new option to the command that can be used to specify
 how many times in a row the message should be printed::
 
+    // ...
+    use Symfony\Component\Console\Input\InputOption;
+
     $this
         // ...
         ->addOption(