minor #6411 Fixed a typo in configuration-block (VarunAgw)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #6411).

Discussion
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Fixed a typo in configuration-block

It is not rendered properly right now (https://symfony.com/doc/current/book/controller.html#route-parameters-as-controller-arguments)

I think this should fix it

Commits
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93618ed Fixed a typo in configuration-block

book/controller.rst

@@ -260,7 +260,7 @@ to ``$name``. Just make sure they the name of the placeholder is the
 same as the name of the argument variable.
 
 Take the following more-interesting example, where the controller has two
-arguments::
+arguments:
 
 .. configuration-block::