minor symfony#9087 Add missing "bundles" sub-dir for third party-bundle templates (floriansemm)

This PR was merged into the 4.0 branch.

Discussion
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Add missing "bundles" sub-dir for third party-bundle templates

Migration Guide is inconsistent at this point. The docs in [How to overwrite bundle templates](https://symfony.com/doc/current/templating/overriding.html#overriding-core-templates) containing the correct template structure.

Commits
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cd8f542 Add missing `bundles` sub-dir

Author: javiereguiluz

setup/flex.rst

@@ -217,7 +217,7 @@ manual steps:
 
    * ``app/Resources/views/`` -> ``templates/``
    * ``app/Resources/translations/`` -> ``translations/``
-   * ``app/Resources/<BundleName>/views/`` -> ``templates/<BundleName>/``
+   * ``app/Resources/<BundleName>/views/`` -> ``templates/bundles/<BundleName>/``
    * rest of ``app/Resources/`` files -> ``src/Resources/``
 
 #. Move the original PHP source code from ``src/AppBundle/*`` to ``src/``. In