minor #11405 Fixed a minor issue in Serializer component (javiereguiluz)

This PR was merged into the 4.2 branch.

Discussion
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Fixed a minor issue in Serializer component

Tiny error, but very visible:

![image](https://user-images.githubusercontent.com/73419/55962867-03208200-5c72-11e9-86b8-10e1229f4a65.png)

Commits
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c4f5f7c Fixed a minor issue in Serializer component

Author: javiereguiluz

components/serializer.rst

@@ -1420,7 +1420,7 @@ and return ``true`` when
 :method:`Symfony\\Component\\Serializer\\Normalizer\\CacheableSupportsMethodInterface::hasCacheableSupportsMethod`
 is called.
 
- .. note::
+.. note::
 
     All built-in :ref:`normalizers and denormalizers <component-serializer-normalizers>`
     as well the ones included in `API Platform`_ natively implement this interface.