minor #15824 [Routing] rewrite incorrect sentence (Ahummeling)

This PR was merged into the 4.4 branch.

Discussion
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[Routing] rewrite incorrect sentence

This bit of documentation: `This feature is called "param converter" and is only available when using annotations to define routes.` Would imply that the param converter is only enabled for routes that are defined through annotations. But I believe this is not case.
This pull request rewrites this sentence and would hopefully prevent other people from also spending a lot of time unnecessarily.

Commits
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55b322d rewrite incorrect sentence

Author: javiereguiluz

routing.rst

@@ -824,8 +824,7 @@ Parameter Conversion
 
 A common routing need is to convert the value stored in some parameter (e.g. an
 integer acting as the user ID) into another value (e.g. the object that
-represents the user). This feature is called "param converter" and is only
-available when using annotations to define routes.
+represents the user). This feature is called "param converter".
 
 In case you didn't run this command before, run it now to add support for
 annotations and "param converters":