Update dependency requirements - allowed Symfony 6 (#23)

Update dependency requirements - allowed Symfony 6

Author: JanMikes

composer.json

@@ -13,9 +13,9 @@
     ],
     "require": {
         "php": "^7.2||^8.0",
-        "symfony/framework-bundle": "^4.4 || ^5.0",
-        "symfony/http-client": "^4.4 || ^5.0",
-        "symfony/http-client-contracts": "^1.0|^2.0",
+        "symfony/framework-bundle": "^4.4 || ^5.0 || ^6.0",
+        "symfony/http-client": "^4.4 || ^5.0 || ^6.0",
+        "symfony/http-client-contracts": "^1.0|^2.0|^3.0",
         "nyholm/psr7": "^1.0",
         "m4tthumphrey/php-gitlab-api": "^11.0"
     },