Update phan/phan version constraints in composer.json (#111)

Allow version 6

Author: mvdbos

composer.json

@@ -25,7 +25,7 @@
         "symfony/event-dispatcher": "^4.0.0||^5.0.0||^6.0||^7.0",
         "vdb/uri": "^0.3.2",
         "spatie/robots-txt": "^2.0",
-        "phan/phan": "^4.0||^5.0"
+        "phan/phan": "^4.0||^5.0||^6.0"
     },
     "require-dev": {
         "phpunit/phpunit": "^9.0.0",