Always use latest Symfony version

Removed the version number of the require command to avoid installing outdated requirements

Author: gbirke

setup/flex.rst

@@ -111,7 +111,7 @@ Symfony application by executing the following command:
 
 .. code-block:: terminal
 
-    $ composer create-project symfony/skeleton:4.1.* my-project
+    $ composer create-project symfony/skeleton my-project
 
 .. note::