minor #17720 [Serializer] Fix default XmlVersion used by XmlEncoder (alexandre-daubois)

This PR was merged into the 5.4 branch.

Discussion
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[Serializer] Fix default XmlVersion used by XmlEncoder

Closes #17717

If you don't give an explicit version, it uses the `\DOMDocument` default one, which is 1.0.

Commits
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13f9766 [Serializer] Fix default XmlVersion used by XmlEncoder

Author: javiereguiluz

components/serializer.rst

@@ -1181,7 +1181,7 @@ Option                          Description
 ==============================  =================================================  ==========================
 ``xml_format_output``           If set to true, formats the generated XML with     ``false``
                                 line breaks and indentation
-``xml_version``                 Sets the XML version attribute                     ``1.1``
+``xml_version``                 Sets the XML version attribute                     ``1.0``
 ``xml_encoding``                Sets the XML encoding attribute                    ``utf-8``
 ``xml_standalone``              Adds standalone attribute in the generated XML     ``true``
 ``xml_type_cast_attributes``    This provides the ability to forget the attribute  ``true``