minor #4441 Updated first code-block:: bash (Nitaco)

This PR was submitted for the 2.5 branch but it was merged into the 2.3 branch instead (closes #4441).

Discussion
----------

Updated first code-block:: bash

The command for executing an console command was wrong. The php command was missing. It will help further readers.

Commits
-------

9f7fda4 Updated first code-block:: bash

cookbook/console/console_command.rst

@@ -59,7 +59,7 @@ This command will now automatically be available to run:
 
 .. code-block:: bash
 
-    $ app/console demo:greet Fabien
+    $ php app/console demo:greet Fabien
 
 Getting Services from the Service Container
 -------------------------------------------