minor #34316 more strict requirements of experimental components (xabbuh)

This PR was merged into the 5.0-dev branch.

Discussion
----------

more strict requirements of experimental components

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       |
| License       | MIT
| Doc PR        |

Commits
-------

23bc40b764 more strict requirements of experimental components

Author: nicolas-grekas

composer.json

@@ -50,7 +50,7 @@
         "symfony/security-http": "^4.4|^5.0",
         "symfony/serializer": "^4.4|^5.0",
         "symfony/stopwatch": "^4.4|^5.0",
-        "symfony/string": "^5.0",
+        "symfony/string": "~5.0.0",
         "symfony/translation": "^5.0",
         "symfony/twig-bundle": "^4.4|^5.0",
         "symfony/validator": "^4.4|^5.0",
@@ -77,8 +77,10 @@
         "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",