minor #12901 [Serializer] Remove note about CsvEncoder as_collection flag (ogizanagi)

This PR was merged into the 5.0 branch.

Discussion
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[Serializer] Remove note about CsvEncoder as_collection flag

This is the default since 5.0

https://github.com/symfony/symfony/blob/ad7d24109c5d9d9bce66ae57c509eb9baa3cc21b/src/Symfony/Component/Serializer/Encoder/CsvEncoder.php#L47
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Commits
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0be5b16 [Serializer] Remove note about CsvEncoder as_collection flag

Author: javiereguiluz

components/serializer.rst

@@ -786,9 +786,6 @@ The ``CsvEncoder``
 
 The ``CsvEncoder`` encodes to and decodes from CSV.
 
-You can pass the context key ``as_collection`` in order to have the results
-always as a collection.
-
 The ``XmlEncoder``
 ~~~~~~~~~~~~~~~~~~