Bumped phpunit dependency

Author: norberttech

composer.json

@@ -25,7 +25,7 @@
         "openlss/lib-array2xml": "^1.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "^7.0|^8.0",
+        "phpunit/phpunit": "^8.4",
         "friendsofphp/php-cs-fixer": "^2.4"
     },
     "autoload": {