Fixed phpunit version

Author: Andrey Helldar

composer.json

@@ -25,7 +25,7 @@
     "require-dev": {
         "mockery/mockery": "^0.9|^1.0",
         "orchestra/testbench": "^3.4|^4.0|^5.0|^6.0",
-        "phpunit/phpunit": "^5.7|^6.0|^7.0|8.0|^9.0"
+        "phpunit/phpunit": "^5.7|^6.0|^7.0|^8.0|^9.0"
     },
     "autoload": {
         "psr-4": {