Allow any versions of the phpunit bridge

Author: nicolas-grekas

composer.json

@@ -7,6 +7,6 @@
         "php": "^7.0",
         "symfony/browser-kit": "^3.3|^4.0",
         "symfony/css-selector": "^3.3|^4.0",
-        "symfony/phpunit-bridge": "^3.3|^4.0"
+        "symfony/phpunit-bridge": "*"
     }
 }