Continuing the unification process across some of YouTube's services and products, YouTube has started combining the YouTube Gaming subscriptions with the regular YouTube channel subscriptions, making it easier to find and watch gaming channels, no matter which app you use.
Now you can subscribe to a channel on YouTube, and you will see that subscription in YouTube Gaming (and vice versa), and you can unsubscribe to a channel just as easily, in either app. You will notice that your YouTube subs feed may also show posts from YouTube Gaming channels, and that notifications will remain separate for each app. Keep in mind that by default subscriptions in the YouTube app will send occasional notifications. To learn more about managing your notification setting, click here.
Users are starting to get notified of this change that should be completed in the next few days. For YouTube's official announcement, click here.