minor change in readme.md

Author: mkwsra

README.md

@@ -72,7 +72,7 @@ You can easily send a message to all registered users with the command
 
 You can send a message based on a set of tags with the command
 
-    OneSignal::sendNotificationUsingTags("Some Message", array("key" => "device_uuid", "relation" => "=", "value" => 123e4567-e89b-12d3-a456-426655440000), $url = null, $data = null, $buttons = null, $schedule = null);
+    OneSignal::sendNotificationUsingTags("Some Message", ["key" => "device_uuid", "relation" => "=", "value" => 123e4567-e89b-12d3-a456-426655440000], $url = null, $data = null, $buttons = null, $schedule = null);
 
 
 ### Sending a Notification To A Specific User