Allow "rawr/cross-data-providers" version compatible with PHP 5.6

Author: JakeQZ

composer.json

@@ -28,7 +28,7 @@
     },
     "require-dev": {
         "phpunit/phpunit": "5.7.27 || 6.5.14 || 7.5.20 || 8.5.41",
-        "rawr/cross-data-providers": "2.4.0"
+        "rawr/cross-data-providers": "^2.0.0"
     },
     "suggest": {
         "ext-mbstring": "for parsing UTF-8 CSS"