actually apply the symfony version constraint

Author: dbu

.github/workflows/tests.yml

@@ -37,9 +37,9 @@ jobs:
       - name: Composer validate
         run: composer validate --strict --no-check-lock
 
-      - name: Globally install symfony/flex
+      - name: Symfony version
         if: matrix.symfony-require != '*'
-        run: composer global require --no-progress --no-scripts --no-plugins symfony/flex
+        run: composer global require --no-progress symfony/flex && composer config extra.symfony.require ${{ matrix.symfony-version}}
 
       - name: Install dependencies
         run: composer update --prefer-dist --no-interaction --no-progress