minor #17907 Adapt CsvEncoder no_headers context (alamirault)

This PR was merged into the 5.4 branch.

Discussion
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Adapt CsvEncoder `no_headers` context

Try fix #15243

Default behavior:
https://github.com/symfony/symfony/blob/c7a7cb8841bb54a68c967b3ea0e57024802b96ed/src/Symfony/Component/Serializer/Tests/Encoder/CsvEncoderTest.php#L45-L60

With `no_headers`
https://github.com/symfony/symfony/blob/c7a7cb8841bb54a68c967b3ea0e57024802b96ed/src/Symfony/Component/Serializer/Tests/Encoder/CsvEncoderTest.php#L647-L653

Commits
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2bfe5da Adapt CsvEncode no_headers context

Author: xabbuh

components/serializer.rst

@@ -1104,7 +1104,8 @@ Option                  Description                                            D
                         with a ``\t`` character
 ``as_collection``       Always returns results as a collection, even if only   ``true``
                         one line is decoded.
-``no_headers``          Disables header in the encoded CSV                     ``false``
+``no_headers``          Setting to ``false`` will use first row as headers.    ``false``
+                        ``true`` generate numeric headers.
 ``output_utf8_bom``     Outputs special `UTF-8 BOM`_ along with encoded data   ``false``
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