Allow flex on composer

Author: loic425

.github/workflows/ci.yml

@@ -37,6 +37,7 @@ jobs:
                 name: Restrict Symfony version
                 if: matrix.symfony != ''
                 run: |
+                    composer global config --no-plugins allow-plugins.symfony/flex true
                     composer global require --no-progress --no-scripts --no-plugins "symfony/flex"
                     composer config extra.symfony.require "${{ matrix.symfony }}"
                     composer config minimum-stability "dev"