simplify flex setup

Author: dbu

.github/workflows/test-application.yaml

@@ -37,12 +37,7 @@ jobs:
               with:
                   php-version: ${{ matrix.php-version }}
                   extensions: 'pdo, pdo_sqlite'
-                  tools: 'composer:v2'
-
-            - name: Install Symfony Flex
-              run: |
-                composer global config --no-plugins allow-plugins.symfony/flex true
-                composer global require --no-progress --no-scripts --no-plugins symfony/flex
+                  tools: 'composer:v2, flex'
 
             - name: Install dependencies with Composer
               uses: ramsey/composer-install@v2