minor #12640 fix supported installable version formats (xabbuh)

This PR was merged into the 3.4 branch.

Discussion
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fix supported installable version formats

see symfony/symfony#34402

Commits
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5ec5438 fix supported installable version formats

Author: OskarStark

setup.rst

@@ -114,10 +114,6 @@ In case your project needs to be based on a specific Symfony version, use the
     $ symfony new my_project_name --version=3.3
     $ symfony new my_project_name --version=3.4
 
-    # use a specific Symfony version
-    $ symfony new my_project_name --version=3.3.10
-    $ symfony new my_project_name --version=3.4.5
-
     # use the most recent 'lts' version (Long Term Support version)
     $ symfony new my_project_name --version=lts