This article explains how you can unsubscribe a group from your "My Groups" page.

To remove a group from the My Groups page, you'll need to unsubscribe from the group.

Unsubscribing removes the group from My Groups and you’ll stop receiving messages from other members of this Group. NOTE: If you own a group, you must first give ownership of your group to another member or delete the group before you can unsubscribe on the My Groups page.