Drop support for Symfony v4

.github/workflows/ci.yml

@@ -17,8 +17,6 @@ jobs:
 
           - operating-system: 'ubuntu-20.04'
             php-version: '7.4'
-            job-description: 'with Sf ^4'
-            execute-flex-with-symfony-version: '^4' # Explicit check for Sf 4.x compatibility
 
           - operating-system: 'ubuntu-20.04'
             php-version: '7.4'

composer.json

@@ -21,16 +21,16 @@
         "composer/xdebug-handler": "^2.0",
         "doctrine/annotations": "^1.13",
         "php-cs-fixer/diff": "^2.0",
-        "symfony/console": "^4.4.20 || ^5.1.3 || ^6.0",
-        "symfony/event-dispatcher": "^4.4.20 || ^5.0 || ^6.0",
-        "symfony/filesystem": "^4.4.20 || ^5.0 || ^6.0",
-        "symfony/finder": "^4.4.20 || ^5.0 || ^6.0",
-        "symfony/options-resolver": "^4.4.20 || ^5.0 || ^6.0",
+        "symfony/console": "^5.4 || ^6.0",
+        "symfony/event-dispatcher": "^5.4 || ^6.0",
+        "symfony/filesystem": "^5.4 || ^6.0",
+        "symfony/finder": "^5.4 || ^6.0",
+        "symfony/options-resolver": "^5.4 || ^6.0",
         "symfony/polyfill-mbstring": "^1.23",
         "symfony/polyfill-php80": "^1.23",
         "symfony/polyfill-php81": "^1.23",
-        "symfony/process": "^4.4.20 || ^5.0 || ^6.0",
-        "symfony/stopwatch": "^4.4.20 || ^5.0 || ^6.0"
+        "symfony/process": "^5.4 || ^6.0",
+        "symfony/stopwatch": "^5.4 || ^6.0"
     },
     "require-dev": {
         "justinrainbow/json-schema": "^5.2",
@@ -46,7 +46,7 @@
         "phpunitgoodpractices/polyfill": "^1.5",
         "phpunitgoodpractices/traits": "^1.9.1",
         "symfony/phpunit-bridge": "^6.0",
-        "symfony/yaml": "^4.4.20 || ^5.0 || ^6.0"
+        "symfony/yaml": "^5.4 || ^6.0"
     },
     "suggest": {
         "ext-dom": "For handling output formats in XML",