minor #17918 [Flex] Replace orm-pack with orm (JoppeDC)

This PR was merged into the 5.4 branch.

Discussion
----------

[Flex] Replace orm-pack with orm

Replace `orm-pack` alias with `orm`.

See symfony/flex#820

> We don't autogenerate aliases for `symfony/*-pack` anymore.

Commits
-------

c589c4c Replace orm-pack with orm

Author: javiereguiluz

setup/flex.rst

@@ -74,7 +74,7 @@ manual steps:
 
    .. code-block:: terminal
 
-       $ composer require annotations asset orm-pack twig \
+       $ composer require annotations asset orm twig \
          logger mailer form security translation validator
        $ composer require --dev dotenv maker-bundle orm-fixtures profiler