fix lowest build by using the very newest phpunit bridge

Author: dbu

composer.json

@@ -36,7 +36,7 @@
         "symfony/browser-kit": "^3.4.4 || ^4.0",
         "symfony/console": "^3.4.4 || ^4.0",
         "symfony/finder": "^3.4.4 || ^4.0",
-        "symfony/phpunit-bridge": "^3.4.4 || ^4.0",
+        "symfony/phpunit-bridge": "^4.2.4",
         "symfony/security-bundle": "^3.4.4 || ^4.0",
         "symfony/twig-bundle": "^3.4.4 || ^4.0",
         "symfony/yaml": "^3.4.4 || ^4.0",