CI: Remove "Require symfony/flex" step from tests

[rosier]

I think this step can be remove since "symfony/flex" is already part of the project dependencies.

https://github.com/symfony/demo/blob/v2.2.0/composer.json#L28

[stof]

This is not the same than before. As a side effect of that step, we were installing deps (as it does not have --no-update, so the next step was running composer update with the Flex plugin active (and so filtering the Symfony packages based on the version filter). after your change, the composer update runs without the plugin.

[rosier]

Looking at the following line I would say that the flex plugin is still active

https://github.com/symfony/demo/actions/runs/3603191289/jobs/6071084273#step:7:133

Is this maybe something that changed with a newer version of composer?

[stof]

Ah, I forgot that recent Flex versions are automatically restarting the composer update when they are installed as part of an update that did not have the filter applied yet.

[javiereguiluz]

Thanks