minor #12069 Fixed a syntax issue in a configuration directive (javiereguiluz)

This PR was merged into the 4.3 branch.

Discussion
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Fixed a syntax issue in a configuration directive

Originally spotted by @TheGarious and reported on Symfony's Slack.

Commits
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c7dd2d6 Fixed a syntax issue in a configuration directive

Author: javiereguiluz

configuration.rst

@@ -291,7 +291,7 @@ configuration file using a special syntax: wrap the parameter name in two ``%``
     by adding another ``%`` so Symfony doesn't consider it a reference to a
     parameter name:
 
-        .. configuration-block::
+    .. configuration-block::
 
         .. code-block:: yaml