minor #8929 Update setup.rst (Sandlayth)

This PR was merged into the 4.0 branch.

Discussion
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Update setup.rst

Change installation symfony commands from 3.3.* to 4.0.*

Commits
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9f0e7a6 Update setup.rst

Author: weaverryan

setup.rst

@@ -30,10 +30,10 @@ In other words, your new app is ready!
     .. code-block:: terminal
 
         # use the most recent version in any Symfony branch
-        $ composer create-project symfony/skeleton my-project "3.3.*"
+        $ composer create-project symfony/skeleton my-project "4.0.*"
 
         # use a beta or RC version (useful for testing new Symfony versions)
-        $ composer create-project symfony/skeleton my-project 3.3.0-BETA1
+        $ composer create-project symfony/skeleton my-project 4.0.0-BETA1
 
     Some version are long-term support (LTS) versions. Read the :doc:`Symfony Release process </contributing/community/releases>`
     to learn more.