Update composer.json

Allow using module on `^6.0.5` phpunit version

Author: evilebottnawi

composer.json

@@ -21,7 +21,7 @@
     ],
     "require": {
         "php": "^7.0",
-        "phpunit/phpunit": "~6.0.5|^7.0"
+        "phpunit/phpunit": "^6.0.5|^7.0"
     },
     "autoload": {
         "psr-4": {