minor #1373 CI: Remove "Require symfony/flex" step from tests (rosier)

This PR was merged into the main branch.

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

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

Commits
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600633d Remove "Require symfony/flex" step from tests

.github/workflows/tests.yaml

@@ -58,9 +58,6 @@ jobs:
                   key: ${{ runner.os }}-${{ matrix.php-version }}-composer-${{ hashFiles('composer.json') }}
                   restore-keys: ${{ runner.os }}-${{ matrix.php-version }}-composer-
 
-            - name: "Require symfony/flex"
-              run: composer require --no-progress --no-scripts --no-plugins symfony/flex
-
             - name: "Install dependencies"
               run: composer update --no-interaction --prefer-dist --optimize-autoloader