[FrameworkBundle] relax conflicts

Author: nicolas-grekas

composer.json

@@ -77,10 +77,8 @@
         "symfony/mailer": "<4.4",
         "symfony/messenger": "<4.4",
         "symfony/mime": "<4.4",
-        "symfony/notifier": ">=5.1",
         "symfony/property-info": "<4.4",
         "symfony/serializer": "<4.4",
-        "symfony/string": ">=5.1",
         "symfony/stopwatch": "<4.4",
         "symfony/translation": "<5.0",
         "symfony/twig-bridge": "<4.4",