Allow PHPUnit ^6 || ^7 || ^8 in composer.json

Author: michalbundyra

composer.json

@@ -19,7 +19,7 @@
     },
     "require": {
         "php": ">=7",
-        "phpunit/phpunit": "8.4.x-dev",
+        "phpunit/phpunit": "^6 || ^7 || ^8",
         "php-mock/php-mock-integration": "^2"
     },
     "archive": {