Limit PHPUnit version

Author: nicekiwi

composer.json

@@ -16,7 +16,7 @@
     "nukacode/database": "^1.0"
   },
   "require-dev": {
-    "phpunit/phpunit": ">=7.0",
+    "phpunit/phpunit": "^7.0",
     "orchestra/testbench": "^3.0"
   },
   "autoload": {