minor #8957 Make require as a dev dependency (theofidry)

This PR was merged into the 3.3 branch.

Discussion
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Make require as a dev dependency

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3027b71 Make require as a dev dependency

Author: javiereguiluz

setup/built_in_web_server.rst

@@ -27,7 +27,7 @@ First, execute this command:
 .. code-block:: terminal
 
     $ cd your-project/
-    $ composer require symfony/web-server-bundle
+    $ composer require --dev symfony/web-server-bundle
 
 Then, enable the bundle in the kernel of the application::