minor symfony#9843 Added a missing versionadded directive (javiereguiluz)

This PR was merged into the 4.1 branch.

Discussion
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Added a missing versionadded directive

We forgot to add this in symfony#9314.

Commits
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f7d96ea Added a missing versionadded directive

Author: javiereguiluz

routing/redirect_in_config.rst

@@ -159,6 +159,9 @@ action:
 
         return $routes;
 
+.. versionadded:: 4.1
+    The ``keepQueryParams`` option was introduced in Symfony 4.1.
+
 .. caution::
 
     Because you are redirecting to a route instead of a path, the required