Remove phpunit.

Author: irazasyed

composer.json

@@ -26,8 +26,7 @@
     },
     "require-dev": {
         "mockery/mockery": "^1.0",
-        "orchestra/testbench": "^3.5 || ^4.0",
-        "phpunit/phpunit": "^7.5"
+        "orchestra/testbench": "^3.5 || ^4.0"
     },
     "autoload": {
         "psr-4": {