This PR was submitted for the 5.4 branch but it was merged into the 4.4 branch instead.

Discussion
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declare Symfony Flex as an allowed plugin

Commits
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8f0f0ca declare Symfony Flex as an allowed plugin

This PR was squashed before being merged into the 5.4 branch.

Discussion
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Enable code blocks

Revert 8f250a2

Revert fb505de from #17020

Tests were broken, see that example from #17098:

```
Run composer config --no-plugins allow-plugins.symfony/flex true
Error: File "./composer.json" cannot be found in the current directory

In ConfigCommand.php line 206:

  File "./composer.json" cannot be found in the current directory

config [-g|--global] [-e|--editor] [-a|--auth] [--unset] [-l|--list] [-f|--file FILE] [--absolute] [-j|--json] [-m|--merge] [--append] [--source] [--] [<setting-key> [<setting-value>...]]

Error: Process completed with exit code 1.
```

[full output](https://github.com/symfony/symfony-docs/runs/7640214086?check_suite_focus=true)

It should not be necessary now that symfony-tools/symfony-application#14 has been merged.

Commits
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7bff8b5 Enable code blocks

This PR was merged into the 4.4 branch.

Discussion
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Fix CI by reverting #17020

The CI is failing in #16992 because of this, see https://github.com/symfony/symfony-docs/runs/7704382531?check_suite_focus=true.

My guess if that it's now fixed upstream thanks to symfony-tools/symfony-application#14.

Commits
-------

7c7c76e fix CI by reverting #17020