minor #11435 Update serializer.rst (yyaremenko)

This PR was submitted for the 4.2 branch but it was merged into the 3.4 branch instead (closes #11435).

Discussion
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Update serializer.rst

you created an endless loop because of not saying in this article that it must be read first:
- this article sends to the 'How to Use the Serializer' article, saying smth like 'if you use the Serializer as a Symfony component, go read there', without saying that this article must be read first,
- and the 'How to Use the Serializer' sends back to this article saying it must be read first

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Commits
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42077d4 Update serializer.rst

Author: javiereguiluz

components/serializer.rst

@@ -38,9 +38,11 @@ Usage
 
 .. seealso::
 
-    This article explains how to use the Serializer features as an independent
-    component in any PHP application. Read the :doc:`/serializer` article to
-    learn about how to use it in Symfony applications.
+    This article explains the philosophy of the Serializer and gets you familiar
+    with the concepts of normalizers and encoders. The examples provided assume 
+    that you use the Serializer as an independent component. If you intend to use
+    the Serializer in the Symfony application, please read :doc:`/serializer`
+    after you finish this article.
 
 Using the Serializer component is really simple. You just need to set up
 the :class:`Symfony\\Component\\Serializer\\Serializer` specifying