minor #15568 Flex: Update links to Symfony 5.3 (Seb33300)

This PR was squashed before being merged into the 5.3 branch.

Discussion
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Flex: Update links to Symfony 5.3

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Commits
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3c6b003 Flex: Update links to Symfony 5.3

Author: javiereguiluz

setup/flex.rst

@@ -189,9 +189,9 @@ If you customize these paths, some files copied from a recipe still may contain
 references to the original path. In other words: you may need to update some things
 manually after a recipe is installed.
 
-.. _`default services.yaml file`: https://github.com/symfony/recipes/blob/master/symfony/framework-bundle/4.2/config/services.yaml
-.. _`shown in this example`: https://github.com/symfony/skeleton/blob/8e33fe617629f283a12bbe0a6578bd6e6af417af/composer.json#L24-L33
-.. _`shown in this example of the skeleton-project`: https://github.com/symfony/skeleton/blob/8e33fe617629f283a12bbe0a6578bd6e6af417af/composer.json#L44-L46
-.. _`copying Symfony's index.php source`: https://github.com/symfony/recipes/blob/master/symfony/framework-bundle/5.1/public/index.php
-.. _`copying Symfony's bin/console source`: https://github.com/symfony/recipes/blob/master/symfony/console/5.1/bin/console
+.. _`default services.yaml file`: https://github.com/symfony/recipes/blob/master/symfony/framework-bundle/5.3/config/services.yaml
+.. _`shown in this example`: https://github.com/symfony/skeleton/blob/a0770a7f26eeda9890a104fa3de8f68c4120fca5/composer.json#L30-L39
+.. _`shown in this example of the skeleton-project`: https://github.com/symfony/skeleton/blob/a0770a7f26eeda9890a104fa3de8f68c4120fca5/composer.json#L55-L57
+.. _`copying Symfony's index.php source`: https://github.com/symfony/recipes/blob/master/symfony/framework-bundle/5.3/public/index.php
+.. _`copying Symfony's bin/console source`: https://github.com/symfony/recipes/blob/master/symfony/console/5.3/bin/console
 .. _`Symfony Requirements Checker`: https://github.com/symfony/requirements-checker