Limit PHP support to 7.4 and 8.0 for Symfony 5

Update requirements to strictly PHP 7.4.x and 8.0.x only (no 8.1+):
- composer.json: php ^7.4 || ~8.0.0
- CI matrix: Remove PHP 8.1, keep only 7.4 and 8.0

This makes symfony-5 a true transition branch between legacy (7.4)
and symfony-6+ which requires 8.0+/8.1+.

Author: toxicity1985

.github/workflows/ci.yaml

@@ -42,9 +42,6 @@ jobs:
           - php: '8.0'
             dependencies: 'highest'
             symfony_require: '5.4.*'
-          - php: '8.1'
-            dependencies: 'highest'
-            symfony_require: '5.4.*'
       fail-fast: false
     steps:
       - name: Checkout

composer.json

@@ -23,7 +23,7 @@
         "issues": "https://github.com/FriendsOfSymfony/FOSCommentBundle/issues"
     },
     "require": {
-        "php": "^7.4 || ^8.0",
+        "php": "^7.4 || ~8.0.0",
         "friendsofsymfony/rest-bundle": "^2.8 || ^3.0",
         "jms/serializer-bundle": "^2.0 || ^3.0 || ^4.0 || ^5.0",
         "symfony/framework-bundle": "^5.0",