minor #4826 Fixed 404 page (SofHad)

This PR was merged into the 2.3 branch.

Discussion
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Fixed 404 page

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | no

On this page: http://symfony.com/doc/current/components/templating/helpers/assetshelper.html#custom-packages

Commits
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c8a8b10 Fixed 404 page

Author: wouterj

components/templating/helpers/assetshelper.rst

@@ -104,4 +104,4 @@ Custom Packages
 ---------------
 
 You can create your own package by extending
-:class:`Symfony\\Component\\Templating\\Package\\Package`.
+:class:`Symfony\\Component\\Templating\\Asset\\Package`.