The Repeat Password field is a part of the built-in template for the page where the user has to enter the team password. Because it's a required field, you cannot merely hide it to prevent it from displaying, as that would prevent anyone from successfully joining the password protected team. The only way to remove the Repeat Password field and prevent it from being required, is to have a Blackbaud developer customize the template for the organization. This would be a paid Services Engagement. If you are interested in pursuing this route, please Contact Support.