You cannot hide your own ratings/reviews, or ratings/reviews from your group page.
On your group’s webpage, ratings for events within your group are displayed. This means that if you have 10 co-organizers who all create events within your group, every rating across all of those events is aggregated to provide an average rating which will appear in the Group Reviews section (see image below). These reviews are displayed in the order of the most recent. Ratings cannot be hidden or turned off.