minor #7399 Mention the "show-arguments" option of the "debug:container" command (javiereguiluz)

This PR was squashed before being merged into the master branch (closes #7399).

Discussion
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Mention the "show-arguments" option of the "debug:container" command

This fixes #7366.

Commits
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dbf1db5 Mention the "show-arguments" option of the "debug:container" command

Author: xabbuh

service_container/debug.rst

@@ -31,3 +31,13 @@ its id:
 .. code-block:: terminal
 
     $ php bin/console debug:container app.mailer
+
+By default, the arguments of the services are not included in the output. Add the
+``--show-arguments`` option to show them:
+
+.. versionadded:: 3.3
+   The ``--show-arguments`` option was introduced in Symfony 3.3.
+
+.. code-block:: terminal
+
+    $ php bin/console debug:container app.mailer --show-arguments