It looks like it is displaying the information that you have for the author’s bio (I don’t think it is the about page). If you go into your theme’s single.php file you should be able to find, or find a file included, that contains “entry-author-bio”. You should be able to delete the section that contains this information. There is probably some HTML and PHP in this area. Be careful because improperly editing PHP could break the site. Alternately, you could delete the author bio from that user’s profile to not show it.