bug #8913 Update the_big_picture.rst (juanmiguelbesada)

This PR was merged into the 4.0 branch.

Discussion
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Update the_big_picture.rst

Require server (symfony/web-server-bundle) only for dev

Commits
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06f06a4 Update the_big_picture.rst

Author: weaverryan

quick_tour/the_big_picture.rst

@@ -47,7 +47,7 @@ Install and run it with:
 
 .. code-block:: terminal
 
-    $ composer require server
+    $ composer require server --dev
     $ php bin/console server:start
 
 Try your new app by going to ``http://localhost:8000`` in a browser!