Adds compatibility with sensiolabs/security-checker ^6.0

Author: michalbundyra

composer.json

@@ -27,7 +27,7 @@
         "php-amqplib/php-amqplib": "^2.0",
         "phpunit/phpunit": "^5.7.27 || 6.5.8 || ^7.1.2",
         "predis/predis": "^1.0",
-        "sensiolabs/security-checker": "^5.0",
+        "sensiolabs/security-checker": "^5.0 || ^6.0.3",
         "symfony/yaml": "^2.7 || ^3.0 || ^4.0 || ^5.0",
         "zendframework/zend-coding-standard": "~1.0.0",
         "zendframework/zend-loader": "^2.0"