minor #8967 Reworded the note about dump() availability per environment (javiereguiluz)

This PR was squashed before being merged into the 2.7 branch (closes #8967).

Discussion
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Reworded the note about dump() availability per environment

This fixes #8731.

Commits
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ab5ac1e Reworded the note about dump() availability per environment

Author: javiereguiluz

templating/debug.rst

@@ -46,8 +46,7 @@ The same mechanism can be used in Twig templates thanks to ``dump()`` function:
         </a>
     {% endfor %}
 
-By design, the ``dump()`` function is only available if the ``kernel.debug``
-setting (in ``config.yml``) is ``true``, to avoid leaking sensitive information
-in production. In fact, trying to use the ``dump()`` function when ``kernel.debug``
-is ``false`` (for example in the ``prod`` environment) will result in an
-application error.
+By design, the ``dump()`` function is only available in the ``dev`` and ``test``
+environments, to avoid leaking sensitive information in production. In fact,
+trying to use the ``dump()`` function in the ``prod`` environment will result in
+a PHP error.