If you're no longer interested in a specific conversation, you can choose to unsubscribe from any future notifications.
In the upper-right corner of any page, click your profile photo.
On your profile page, click the Repositories tab, then click the name of your repository.
Click either the Issues tab or the Pull Requests tab for the repository.
In the sidebar on the right, click Unsubscribe.
Once you unsubscribe from a conversation, you will no longer receive any notifications about the thread. However, if you or a team you're on are @mentioned, you'll once again start receiving notifications.