config(queue): default to redis driver

Updates the default `QUEUE_CONNECTION` value to be `redis`
instead of `sync`.  This can cause problems if users skip
the initial setup or select the prefilled options rather
than the recommended ones.

Closes pterodactyl#4660

Author: matthewpi

.env.example

@@ -23,7 +23,7 @@ REDIS_PASSWORD=null
 REDIS_PORT=6379
 
 CACHE_DRIVER=file
-QUEUE_CONNECTION=sync
+QUEUE_CONNECTION=redis
 SESSION_DRIVER=file
 
 HASHIDS_SALT=