minor symfony#8619 Change some word choice, 'complex' instead of 'complicated' (seydu)

This PR was submitted for the master branch but it was merged into the 2.7 branch instead (closes symfony#8619).

Discussion
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Change some word choice, 'complex' instead of 'complicated'

Commits
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c82f6a7 Update serializer.rst

Author: wouterj

components/serializer.rst

@@ -21,9 +21,8 @@ the middle. This way, Encoders will only deal with turning specific
 **formats** into **arrays** and vice versa. The same way, Normalizers
 will deal with turning specific **objects** into **arrays** and vice versa.
 
-Serialization is a complicated topic, and while this component may not work
-in all cases, it can be a useful tool while developing tools to serialize
-and deserialize your objects.
+Serialization is a complex topic. This component may not cover all your use cases out of the box, 
+but it can be useful for developing tools to serialize and deserialize your objects.
 
 Installation
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